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START AT THE BEGINNING We're not talking about saving a few minutes by doing basic troubleshooting instead of guessing. We're talking about many hours of wasted time, when you could have found the problem quickly by just starting at the beginning (I speak from experience!). In order to start at the beginning, you need to have a clear picture in your mind of how the gizmo you're fixing is connected, so you know where the beginning is and the next thing to check. To fix a phone line, it might be the telephone company or channel bank to the NI (Network Interface), to the lightning protector and ground, to a mod jack, to the CO line card, to the CO line (or system wide) programming on the system for things like attenuation, impedance, echo cancellation, and CPC, etc.

You also need to think about any external stuff connected to the phone system, like the AC power, battery backup, ground, other phone lines, stations, paging etc. All of the external gizmos connected to a phone system can be causing a problem on the phone system - so you want to get them disconnected to make absolutely sure they're not causing your problem. If you leave out something, Murphy's Law says that will be the problem (that you'll find many hours later). Making yourself a list or drawing a picture of how everything is connected might be a good idea when you walk into the job

Simply stripping a system down and adding everything back one thing at a time until the problem returns, is the best way to troubleshoot a problem. I know you don't want to do this. You'd like to poke around at the easiest stuff first. You can do that, but if you find the problem it will usually take longer than if you started at the beginning and did your troubleshooting in a methodical manner. Fixing a system today by stripping it down and starting at the beginning is much easier than in the old days of 1A2 (with 25 to 100 pair cable). On a 1A2 system, you could have 30 or more phones that were all the lines were bridged together. If a line wasn't working right, you could disconnect the line card in the 1A2 system from all of the phones by pulling one set of jumpers. If the problem went away, one (or more?) of those 30 phones had a problem (often a water damaged 25 pair connector that got wet when mopped).

You could guess at which phone it was and start taking apart connectors to see if they were green inside (you couldn't see the water damage from the outside), and if you got it on the first five tries you would have gone out and played the lottery. It was your lucky day. The only reasonable way to find the problem was to start removing the 3 pair jumpers to a line on a phone, one at a time (marking them so you could put them back in the same position on the 66B block). Remove a jumper, test to see if the problem cleared, and if it didn't go on to the next jumper. If it cleared, you trace that jumper to the cable, then look at the floor plan to see where the cable was. If you were having a really unlucky day, the bad phone was the 30th jumper.

Modern systems are much easier!
So you've got a strange problem. Since you've probably got dozens or hundreds of the particular model of system you're working on installed, and the problem isn't occurring at those other places, there must be something different about the place you're at. All you have to do is find what's different! Phone system hardware (from traditional phone system manufacturers) is more dependable than ever. The cards and power supplies just don't break like they did in the 80's and 90's. While the problem you're looking at might be caused by a bad card or power supply, it may just be an interaction with something that's connected to that particular phone system, at that particular site.

Since the phone system by nature has to connect to the outside world, the interface to the outside world is likely to be causing some problems. It's easy to check the power on a system by simply running the system on the battery backup to see if the problem clears (it's not a bad idea to carry a cheap battery backup in your truck for testing). Removing the system ground is also a good thing to do. The AC ground is already disconnected as soon as you pull the plug from the wall on the battery backup/UPS, to run the system on batteries. Unless you put it in yourself, it's hard to know whether a ground is good! Just because it's a green wire, it doesn't mean it's actually connected to a good ground, or even anything at the other end. Fixing an odd problem could be as simple as reversing the tip and ring on a CO line (especially from a channel bank or VoIP box), an external page port, external bells, or an MOH/BGM port. Ground loops can cause strange problems. Leaving one external device connected to a system that you thought you had stripped down could cost you hours. Although it might seem logical to assume something in your troubleshooting process (like "I've never seen one of those go bad" or even "The AC outlet must be wired right"), assuming anything without checking it in its turn in the troubleshooting process has led a lot of guys to chase their tails for hours or days.

We can all remember chasing our tails
We can all remember chasing our tails! Just about every time I've assumed something, I got sidetracked and the problem took longer to fix. Sure, I still do it sometimes (it's human nature), but not very often. While it might sound harder to always Start at the Beginning, you get used to troubleshooting that way and wonder why you wasted all that time in the past! One other thing... Always try your new tester at your office or home before trying to use it at the customer's site! Once you know what your meter readings are supposed to look like, you'll feel confident using testers to solve your customer's problems.

If you remember, believe, and practice what you've just read
If you remember, believe, and practice what you've just read... you'll be able to fix anything! I've walked into a lot of jobs where the system was down, and the customer was going nuts. If I took the queue and started acting nervous and stressed, things would have gotten worse. When I go on a service call the only thing I know for sure is that the problem can be fixed. There's no question about it. That pretty much gets rid of the stress for me, even if the customer is acting nuts. On the drive over to the service call, I get a picture of the system in my mind, and think about where to start and how to proceed. I do get screwed up occasionally when the person who took the service call wrote down the wrong problem, or didn't ask enough questions. Sometimes I'll call the customer when I'm on the way just to verify the problem (and let them know I'll be there shortly). Sometimes I'll go pick up some parts before I go on the call. The amount of traffic in bigger cities makes it pretty tough to go back to the shop for parts, as it would in a more rural area where it might be a 100 or more mile drive.

I personally would never agree to service a system that I didn't have spares for. If you need the spares from the trade-in on a system you're proposing, that's a good reason to give someone a good price on the trade-in. It's still going to be pennies on the dollar. Considering how many used systems are out there from brokers (or ebay), having a whole working system (with at least one station and trunk card) as a spare isn't expensive. It turns a stressful job (telephone repair) into a fun job. You don't need to have every software revision, just something to do troubleshooting and substitution with, and something to get the customer up and running until you get the right software version. Most Interconnects can't have full systems as truck stock for every type of system in your base. If you have a few trucks, it's not a bad idea to keep one type on each truck, so they can bring it over where needed. Making a deal with a cab company or delivery service to deliver a KSU, common cards, and power supply to a job site in an emergency is also a good idea (as it is when you forget something on a cutover).

Every Interconnect has to deal with the problem of bad cards getting mixed up with good ones. In the heat of battle, while you're swapping cards, it's not hard to lose track of them since they all look the same. I carry both gray electrical tape, and tags with string (don't use tags with wire!). The gray tape is easy to stick on a card or the bottom of a phone, so I can write down what I did and the date and time I did it when I swap something. If there isn't already a tag on a card I take out of truck stock, I put some tape or a tag on it so I know it was from the truck. If you do lose track of which card is which, having the whole system lets you test the cards in your shop before returning them to stock. There's nothing that screws up a repairman more than having bad cards for spares. It's something to avoid at all costs. I get a lot of calls from guys asking me all of the possible things that could cause a problem before they even go on a service call. Then they want me to give them the solutions to each possible problem. That would be really hard! You're causing yourself an incredible headache to do that before a service call. You've got to start at the beginning, find the cause of the symptom, and then start trying to figure out what's causing it. Every service call I go on is a challenge, but it's fun because I know it'll be fixed soon, and I get to go on to the next job. It's kind of like being a detective and surgeon in one job - but a lot safer! What scares me is seeing a doctor that doesn't know how to troubleshoot... And there are a lot of them out there.

Troubleshooting Telephone Lines
Disconnect the phone line from the equipment and test the line with your Butt-set. That's basic troubleshooting, but there's more reasons to do it than just to see if it's the Phone Company's problem. A Butt-set (or old 2500 set) is line powered, so it has no reference to ground or AC. That's important, since some of the problems you encounter will be an interaction between the phone line and the telephone equipment, caused by the telephone equipment's reference to ground and "foreign" voltages (like 110VAC). Every phone system will be slightly imbalanced. That means either the tip or the ring is longer than the other side of the pair, or it can have a small foreign voltage on it from being connected to the phone system. In most cases, this doesn't cause a problem. In some, it does - and those are the cases you'll be on. Calling the Phone Company and asking them to "Check the Line" or take readings for you is generally a waste of time. They're trained to say "It tests OK" no matter what. If there's a problem with a Phone Company (CLEC or ILEC) line, it's generally your responsibility to tell the Phone Company exactly why the line is bad. If you give them the numbers, they generally won't bullshit you. Hey, if everybody could do this, they wouldn't need us!

A common trick from Phone Company repairmen is to tell you that your phone system is imbalanced or putting out a foreign voltage or ground.. The testers they use are made for testing lines that aren't terminated. When they hook up their meter (that's made for testing unterminated lines), they're reading the phone system as well as the copper wire. They're supposed to open the line going into the premise before doing most tests so they don't read the CPE (phone system) - which will always read something strange compared to a regular 2500 set (that has no reference to ground or foreign voltage). I've seen Phone Company guys tell the customer they're disconnecting the line going into the building because it's damaging the telephone network. What a bunch of bull. Some of their test equipment will "stress test" the line, which puts out a pretty high voltage/current to try to cure problems with a copper cable. Although that usually won't hurt a phone or system, they're supposed to disconnect the CPE before they do the test. As you can guess, most Phone Company repairmen don't disconnect the CPE. They don't care. They don't have to. Fixing phone line problems is usually as simple as finding what's different about that line(s) that's having the problem, compared to others working in that system at that or at another premise. It's as simple as taking some readings (testing), and comparing the results to other lines at that premise, or at your other customers' sites.

Don't replace the KSU first!
This is what I would do first on a strange case of trouble. I've seen a lot of strange stuff, but there's no way I'm smart enough to fix a strange problem without taking some measurements to lead me in the right direction. Once I find the solution, I might try that on the next case of trouble that's exactly the same - but you can really chase your tail for hours if you don't take a couple of minutes to take some basic readings.

It's as easy as taking the readings for on and off-hook DC voltage, loop current, AC, CPC, and Circuit Loss, and writing the results down on a piece of paper. This lets you compare the results to other lines at the same premise, and at other (working) sites. The problem will probably just jump out at you, and you'll know what to look at to fix the problem. Filling out this chart is very important these days because customers are switching from the LEC (or ILEC - Incumbent Local Exchange Carrier, or the real Phone Company) to a CLEC (Competitive Local Exchange Carrier, like Mike's Phone Company). In most cases, the customer doesn't call you up to ask if it will work OK. They make the change to save a few bucks, and call you when things don't work right (and then spend the next two years' savings on your T&M). By having a chart of the readings for the old LEC, you'll have a basis of comparison when the customer switches the lines to a CLEC and they don't work right.

Instructions: The only way to diagnose many problems on phone lines is to take voltage, current and circuit loss readings. When you have a problem, by taking readings on all of the phone lines at a premise, and comparing the results to those at other premises with no problems, the cause of the problem should jump out at you. Always take readings at premises where you aren’t having problems first, so you have a basis of comparison, and a comfort level with your readings. Never use a tester for the first time at a premise with a problem! In most cases, if you ask the phone company to take these readings, they will simply say “they’re fine.” They don’t care. They don’t have to. It’s your customer, your problem, and your money. Once you’re armed with readings that may point to the cause of the symptoms at a particular premise, going to battle with the phone company is a lot easier. Even with these reading, you may have to escalate the case of trouble, since the repair people at the phone company may not know what these readings mean.

NOTES: When taking Circuit Loss readings for a “Can’t Hear” or “Can’t be Heard” problem, you must use the 1KC (milliwatt) tone for the local CO these lines are working from. If the lines are from a CLEC or on portability, you must find the 1KC tone number located at the CO these lines originate from. Using any other 1KC number will give you incorrect circuit loss readings and be meaningless, since there is always an unknown amount of loss between Cos If there are three or more phone lines at a premise and you have a 1KC Tone Generator, you can do a “Loop Around” test, sending tone on one line, and receiving it on the others. Doing some math, you can get within about 10% of the actual circuit loss on the lines. If the there is more than 8.5db of loss on a line, the phone company has to bring it up over -8.5db (except at true Rural phone companies, where they can do anything they want to get you dial tone). Since “Can’t Hear” problems start at around -7.5db, you’ll have to change the line to a trunk (with a minimum -5.5db spec), or find a way to amplify the line yourself. 2. The phone company doesn’t have to bring the Loop Current on a phone line down unless it’s over 110maDC. Since problems start occurring above 35ma (sometimes over 27ma), you’ll have to reduce the Loop Current yourself. If the current is below 23ma, it’s the phone company’s responsibility to get the current up over 23ma (except at true Rural phone companies).

NOTES: 3. The phone company doesn’t have to bring the AC on a phone line down unless it’s over 50VAC (for safety reasons). Since problems start occurring on telephone systems above .5VAC, you’ll have to reduce the AC yourself. 4. Some phone lines give a brief open loop (0VDC) when the line first goes off-hook, or right after the last digit is dialed. This can cause a cut-off if the CPC (Open Loop Timer) in the phone system is set too low. The CPC signal is normally 550 to 850ms at 0 volts, so the CPC or Open Loop Disconnect timer on a phone system should be set to 500ms (or shorter than the measured CPC signal). 5. Echo problems are usually caused by an impedance mismatch between the trunk and station equipment. Since there is no easy way to measure the impedance of the phone line or phone in the field, the only way to check is to change the impedance to see if the problem clears (using a 600 to 900 ohm Impedance Matcher).

You should also check the programming or jumper options for the trunks or trunk cards. You'd want to check the Open Loop Disconnect (CPC) time, any impedance settings (like 600 or 900 ohms), attenuation settings, echo canceller settings, and anything else that can effect the operation of a trunk. You will need to know the location of a Central Office, the type of CO, who owns the CO, or even how far the premise is from the local CO In my opinion, you should automatically fill out the Telephone Line Diagnostic Table for every new installation, whether you're having problems or not. I actually recommend taking the time to do it before you propose a system, so you know if you're in for trouble before you quote the new system! It won't take long before it will take you just a few minutes to fill out the chart, and potential (expensive) problems will just jump out at you. My suggestion is to use an Installation Checklist before every job you propose. Customer's can have expectations about their phone system that they forget to tell you, or your system may just not do something the customer assumes it can do. Using the Installation Checklist can really prevent arguments, especially the ones where the customer says he won't pay you!

If you're not excited and stressed (or don't show it), even with the customer breathing down your neck, the customer will have less stress and probably let you do your work. If you explain to the customer what you're doing (show him your chart?), and why you're going about it in the manner you are, that might go a ways to calm an excited customer down. And then again, some customers are just going to figure that every phone man knows magic, and should be able to fix

Loop Current & Circuit Loss
Loop Current is the amount of electrical energy flowing through the telephone and line, as opposed to the voltage which is the force behind the energy. There is a definite correlation between the Loop Current and Line Voltage (Ohm's Law), but the loop current reading is often what indicates the problems in telephony... not the voltage reading. The carbon transmitter used in telephones has been the controlling factor for years, since it needs over 20ma to sound good.

THE PROBLEM: . Until about the mid 1980's, the big problem with loop current was that it was often too low. That was when the only way to get from point A to point B was a pair of copper wires. Now, with the proliferation of electronic Central Offices and electronic pair gain equipment: T1, Fiber Optics, Remote Central Offices and SLICs in every suburban and even rural area (you can see these Huts and Buried Vaults scattered around everywhere), over 90% of the problems are high loop current. This is because the manufacturers of the "far end" pair gain equipment have adhered to a very old specification for loop current, but one that is still valid, that says between 23ma and 120ma are OK - but the CPE is much closer to the source of the talk battery than the old days. When the phone company tells you that they are within specs (while smoke wafts off your trunk cards at 80ma of loop current), they're right!

Both the phone company and CO equipment manufacturers have no incentive to bring the loop current down. All they have to do is make a standard 2500 set work (which has no active electronic circuitry to burn up), and the farther out it works... the better. Until the FCC sets a new standard for high loop current (unlikely), or CPE manufacturers take account of the high loop current problem (seems unlikely), the Interconnect company will be left holding the repair bag for these problems. Most CPE equipment was designed based on low loop current problems... it works well right down to 23ma. CPE manufacturers have been really slow to try to head off the high loop current problem. In the rare case of low loop current (below 23ma), the phone company is required to bring it up to 23ma.

The main problem created by high loop current is heat. The components on the trunk card or telephone that connect to a CO line with high loop current get hotter than the manufacturers planned for. When the components get hot, their specs change, which makes the circuit work differently - usually with unpredictable results. If the loop current is high enough, a component can get fried and the device will stop working instead of just having problems. Eventually, the heat from the high loop current can damage one or more components on a trunk card, shortening the life of the card. BACKGROUND: Phone wire used to be much bigger than the 24 gauge standard today, so they could carry current the long distances that needed to be traveled from the CO (Central Office). There is a definite loss of electrical energy per foot of copper wire. The closer the CO got to the subscriber's location (because there are more and more COs these days), the less there was need for the current carrying capability of the bigger wires. Since the 1960's, phone wires have gotten smaller, except in rural areas where the distance to the subscriber still requires the bigger wires with larger current carrying (and lower circuit loss) capabilities. Keep in mind that some very rural CO's operate on their own totally different voltages and currents to get the phone service to their subscribers (like 100VDC talk battery).

At the end of a long loop, the current that left the CO at 35ma might be 18ma because of wire loss (resistance), and the audio level may be well below -8.5db, causing it to be hard to hear. The circuit loss (volume) can be given a boost by the phone company by putting load coils into the loop, usually on loops over 3 miles. The load coil uses inductance to increase the audio voltage (sound level) at voice frequencies, while rolling off higher frequencies. If you need to use the higher frequency capabilities of the phone line for high speed data (like a 56K modem or DSL), you may have to get the load coil removed to allow those higher frequencies to pass through (although the voice capabilities of the line may then be unusable due to the distance). Data circuits have always been adjusted 13 db below voice levels (they like lines with low volume). In some cases, the Phone Company screws up and there's a misplaced load coil on the pair, either too close to the premise, too close to the CO, or not needed at all. Although everything is computerized, a lot of the plant records indicating which pairs have had load coils put on them in the past are incorrect. That means that when someone gives up a line that needed a load coil, and the pair is re-used, the Phone Company might not know the load coil is on that pair, and it could create a problem on the new phone line that pair is used for. Mis-placed load coils will change the impedance of the line and could even make it too loud, which can distort both voice and DTMF digits (causing voic DTMF recognition problems).

A special TDR (Time Domain Reflectometer) can see the load coils on a phone line, and pinpoint the exact number of feet from the premise. If you're having strange problems, especially with DTMF recognition, it's not a bad idea to ask the phone company to check the line for mis-placed load coils. Most TDRs can see out to the first load coil on a line. A special TDR (more expensive) can see out to 5 or more load coils. Phones Companies use another piece of equipment that causes strange problems... Pair Gain Equipment. Phone companies today have little or no interest in putting more copper in the ground. If a premise has a six pair going to it from the nearest pedestal, and the subscriber needs seven lines, the Phone Company has two choices, bury more copper cable, or use an electronic gizmo to get two lines from one of the existing pairs.

A voice T1 is simply pair gain equipment, getting 24 lines from one or two pairs of copper. A T1 is expensive because the signal needs to be repeated every 6,000 feet. In the case of a lack of facilities (copper) to a particular building, the copper pairs usually aren't going very far from the pedestal or pole to the premise, and they usually don't need to very many lines, so some fairly inexpensive electronics can split a single pair of copper into two or more lines. The problem with pair gain equipment is that it sometimes does a crummy job of emulating a real phone line. This stems from the old telephone company philosophy (excuse) that they will only guarantee that a line works with a regular 2500 set, and a 9600 baud modem. The reality of the world is that there are almost no 2500 sets connected to any Phone Company's lines, and almost nobody that wants their modem to connect at a slow 9600 baud. But they don't care. They don't have to. It's your job to make your system work with whatever lines they provide.

Some pair gain systems are known for putting out noise (common mode noise that you can't hear, but that's fixed with our Modem Filter), having problems with Caller ID, or various other problems - especially with high speed data (they usually won't pass anything over 24K). Reading the loop current and voltages on the line might point out where the problems are. In some cases, you may be able to get the phone company to switch the pair gain equipment to a different set of lines, if your customer is using a particular line for a special application (like a fax, modem, etc.). The Phone Company won't tell you that they're going to put pair gain on a line. You find out when there are problems, usually after adding a new line, and the readings you take on a couple of lines look different than the other lines. The Phone Company may put pair gain on one or more lines without telling the subscriber, and with no new orders for the subscriber. There may be a new tenant moving into the building, and they're out of pairs, so they put the pair gain equipment on an existing tenant's pairs in order to give service to the new tenant. You have absolutely no control over that, and can't complain about it. The Phone Company can do whatever they want to get dial tone to the NI. CLECs make it very difficult to get problems resolved on telephone lines. They often use the LEC's copper, so they have little or no control over what happens, and often won't offer the same level of service as the LEC. Most won't offer a trunk, which is conditioned better than a line, and can fix strange problems

UNFIXABLE DATA PROBLEMS: Generally speaking, loop current above 27ma will cause problems ranging from intermittent garbage to "no connect" on modems. It's going to be different in every case, so you have to keep loop current in mind as a possibility when you have a problem. I've been able to fix some of these problems by using a different brand modem, but it's not convenient to carry around a box of modems for testing. A customer called me about a location with an AT&T System 75 switch with single line stations, where the users were having trouble connecting or getting garbled data intermittently with laptop computers and modems connected to the single line station ports. The loop current wasn't super high, I think it was in the 35 to 40ma range, but the installation of Loop Current Attenuators at the frame for those stations using laptops solved the data problems by reducing the loop current below 27ma. Loop current problems are not limited to CO lines. They also can occur on PBX or Key System single line station ports. Since fax transmissions are just high speed data, it's common for high loop current to cause problems with fax machines. Keep in mind that some station ports are 24VDC, instead of the normal 48-50VDC voltage of a CO line. The same loop current specifications apply to the lower voltage... between 23 and 35ma.

COMMON SYMPTOMS OF HIGH CURRENT: Most phone systems work OK with loop current in the 23 to 35ma range, although there are some that will cause problems above 27ma. One that comes to mind is the Walker Poet. One of our customers reported that he had intermittent crosstalk, even after replacing everything - KSU, cards and power supply. Walker tech support suggested that he check the loop current, which was found to be 32ma, normal in most cases. Walker said to get the current down to 27ma or less, and the problem was cured. In one case on another type of phone system, crosstalk was repaired by replacing the trunk cards, but the problem kept reappearing. Constant high current would eventually break down (damage) the components on the trunk card, and crosstalk would return. There have been numerous reports of memory failures in equipment like dialers, faxes and answering machines. .

Many CO line (Trunk) cards are burned up on all types of systems every day... some under maintenance and some billable. In some areas, the loop current is running in the 80 to 105ma range. At that point there's no way you can make money with a maintenance contract without a Loop Current Regulator on every line! If you're going to be installing a T1 Channel Bank, verify that the loop current is down at a reasonable level before committing to it, or you could burn up the trunk cards in your phone system. Most modern Channel Banks have reasonable loop current, but it's worth checking to prevent problems later. I've had a number of calls from Long Distance dialer providers whose dialers had all kinds of strange problems with high loop current. Likewise, the payphone industry seems to be hit hard due to the sophisticated electronics in their phones, and the high speed modems they use to transmit call detail data.

Symptoms of High Loop Current Include: Burned Out Key, PBX or Data Equipment Garbled Data and Modem Failures Cut-offs & Squealing on Lines Crosstalk, Echo & Hollow Sounding Lines Numerous Intermittent Circuit Failures Off Premise Equipment Problems Symptoms of Low Loop Current Problems: Poor Voice Transmission Quality & Low Volume Ghost Rings Wrong Numbers Lost Calls During Transfer Data Loss Considering the problems that loop current can cause, if you have weird unexplained problems you should probably go right out and take a reading on the lines... it's easy!

MEASURING LOOP CURRENT: Loop Current & Circuit Loss

Measuring the loop current is easy ou can use a good quality DIGITAL volt-ohmmeter with a DC milliamp scale. An analog meter, except one designed for telephone work, will usually not give you accurate readings. A Fluke, or a few of the Radio Shack meters will do OK - within a couple of ma. The connection diagram for a meter (above) shows the meter in-series with the telephone instrument or system. That will give you the most accurate reading with a meter, since it's going through a 600 or 900 ohm instrument (or Butt-set). As an alternative to connecting the meter in-series with the instrument, you can just short the pair with your meter leads in the ma mode, and read the direct loop current, which will probably be a couple of ma higher than the reading through a phone, but it might get you close enough to make a decision on what to do.

If you try to use resistors to bring the current down, you really need to watch the db loss as you increase the resistance, so you don't get it too low to hear properly. Try to stay above -7db. Below that you'll have a hard time hearing on long distance calls. Generally speaking, for every 100 ohms you put in-series with the tip and ring (you have to keep the line balanced and put the same value resistor on both sides of the line), you'll drop the loop current by 1ma, and the circuit loss by 1db. That means if you want to get down to 30ma from 35ma using 500 ohm resistors, you'll lower the volume of the line by 5db - and you probably won't be able to hear well. As was stated before, to measure loop current with a regular meter, you need the meter in-series with the telephone line and telephone. To measure voltage, whether the DC line voltage or the AC audio voltage, you need the meter in parallel (across) the telephone line. You don't want to make a mistake in your hook-up as the readings would be meaningless (and could cause you to take an expensive improper action). Make sure you meter is set on DC ma, not AC ma!

To hookup a regular meter to measure loop current in-series: If you have bridging clips on a 66 block, just open one of them, and connect one lead of the meter towards the CO, and the other towards the equipment. It doesn't matter which color lead goes where since the meter will display a + or - that you don't care about (except on an analog meter which will make the needle go backwards and get damaged). With the line on-hook, you should see almost no current flowing through the meter (it will read maybe .01ma). When you go off-hook with either the phone equipment, modem, or your butt set, you should get a reading of between 23 and 35ma if the line is OK. Repeat and record the readings for each line, since not all of the lines have loop current problems in many cases.

REDUCING THE HIGH LOOP CURRENT: If you have a high loop current reading, you have three choices: Do nothing Put resistors on the line, keeping in mind that too much resistance will lower the volume of the line too much Put a commercially available Loop Current Regulator or Attenuator on the line The only two choices are obvious. Most opt for the commercially available Loop Current Regulator. Examples of commercially available Loop Current Regulators

One is modular while the other two are line versions which can be plugged inline with the RJ-11/RJ-14 either for testing - or for good, and a 66 Block version which can be plugged on to a split 66 M block (4 pins across, split), taking the place of the bridging clips. You can also punch down the modular versions by cutting the modular cord. The Loop Current Regulators are all automatic. Just plug it in, and it brings the current down to 25ma with no loss of audio level on the line. They are the easiest to use. The Loop Current Attenuator has a set of four dip switches. You flip one at a time (in some combination) while watching the loop current come down to below 27ma on your meter (but above 23ma). At that point you just leave it, and it's fixed. You do need to buy one Attenuator per line that has high loop current. It will not reduce the volume level of the line, like resistors would. I've actually flipped the switches on the Loop Current Attenuator while watching a thousand cycle tone from the CO, and the audio level actually went up a hair all the way down to 20ma...That's pretty amazing! Don't mistake the Loop Current Attenuator for an audio attenuator (pad). Audio Attenuators are used to reduce the audio level of a line (db) along with the DC loop current, usually by a fixed amount printed on the device, when the audio level of the line is too high.

Most phone guys don't like playing with resistors, but if you'd like to try, here's what you've got to do - and it will work in some cases. As an example, many phone systems will get a squeal when two lines on the system are conferenced together if there is high loop current (and sometimes a loud line). Many years ago, TIE suggested replacing the bridging clips with 100 ohm (or whatever works) resistors to cure the squeal problem. It worked like a charm on every system I've tried it on, and I just used Radio Shack 100 ohm 1/2 watt resistors in all cases (1 watt resistors would be safer). I figured that putting resistors in-series with the line couldn't help the volume of the line, so I tested it with a phone at the KSU by listening to the thousand cycle tone, and using alligator clips to jump out the resistors. I couldn't notice a big drop, so I figured it was OK. In some cases of high loop current, the audio level is already high, like -4db, so you have some room to fool with resistors before the line isn't loud enough. If you're already at a -6 or -7db, you really don't have any room to play with the audio, and you should probably go right for the Loop Current Regulator which has some electronics to keep the level up.

A PRIMER ON TELEPHONE LINE AUDIO LEVEL (db): One of the more common complaints that a telephone man hears is "Can't Hear". It may have been on only one call to Zanzibar, but here I am on a service call and I've got to talk nicely to the customer. One of the problems with this service call is that I'm usually pretty powerless to do anything about it anyway, but I can't tell that to the customer. Here's a little information that will let you actually do some testing if you think there really is a problem. Since you talk on your Butt-set all day, you probably have a good enough ear to be able to tell if a line isn't as loud as it should be. The ideal level for a telephone line loop loss seems to be about -5.5db. Local calls aren't too loud, and you can still hear OK on intercity and long distance calls, which have a lot of loss compared to local calls. The farther you get from the Central Office, the lower the volume is going to be on a call.

The first thing you need is a db meter. Either use one designed for telephone lines, in which case an analog one is OK, or get a digital unit. The impedance of the line, be it 600 or 900 ohms seems to make a difference to some extent. Telephone Circuit Loss Testers are made for this use, but I've found that even the Radio Shack digital meters that have a db scale are OK, especially if you compare it to a "real" meter to get an idea of what kind of a difference in readings you will see. Once you use it on a few jobs, you'll get a feel for what you're looking at. When you are measuring the db loss of a line, you're reading only the AC component - the audio - of the phone line. At the same time, there is the DC talk battery component of the phone line of about 48VDC. Of all measurements, the DC voltage seems to be the one that you really shouldn't worry about (the voltage will follow the current... according to Ohm's Law). As I stated earlier, you connect a meter in parallel (across) with the telephone line to read db. When you're trying to attenuate loop current by using resistors only, it's imperative that you have two meters, a meter to read the loop current and a meter to read the resistors' effect on the db loss, so you know whether it's gone too low to be usable (anything below -7.5 db would be hard to hear). You could use the same meter by changing the lead configuration and range, but that gets time consuming and frustrating. Since loop current measurements are not usually exactly the same line to line, you should repeat the process for each line. If you assume anything (like the loop current or circuit loss is the same on all the lines), it'll come back and get you!

The ideal db loss to look for is -5.5db, when calling the 1000 cycle test tone from the local CO. If you use the tone from another Central Office, you won't be able to tell the real loss on the line, since there is an additional (unknown) loss from CO to CO. I believe that the phone company is required to give you the correct phone number to use. In Chicago, there used to be a Test Line Coordinator who would give out these numbers all day long. They got rid of him, along with the Telephone Museum on Washington Street, years ago. There are also numbers for silent termination, but CO specific silent termination numbers aren't important - you just want to have a nice quiet line to see if there is static or noise etc. on the local loop. They used to have ring back numbers here in Chicago, but they've done away with them years ago (they sure were handy for checking ringing!). That same ringback number had a couple of other neat features... it would beep once if you dialed the touchtone numbers correctly from 1 to 0,*,#, and had a rotary dial speed test built in. These features aren't very important today since electronic dials seldom go off frequency.

To see the effects of using the wrong test tone, dial up the test tone from a CO across the city. Then dial a test tone farther away, and then long distance to another city. I've been able to check the loss of various long distance companies by calling the same test tone (like in New York), through AT&T (10288), MCI (10222), Sprint (10333) etc. You usually get a couple of db loss across town, and 5 or more db loss long distance... which is fine as long as the line started at a -5.5db. If you start with a line at -8.5db, which is the minimum that the phone company has to provide on a "line", that extra 3db loss makes it very hard to hear long distance.

There are two classes of phone lines that you can order from the telco. If you need to bring up the volume of a phone line, changing it to a trunk is about the only way to do it. A "Line" must be maintained by the phone company at -8.5db or greater. A "Trunk" must be maintained at -5.5db or greater, and can be either loop or ground start. I've had the phone company switch over quite a few customers with lines that were below -7 or -8db, to trunks. The phone company then re-engineers the lines (adding loading coils or whatever) to bring it up to -5.5db. That 2 db can really make a difference if you talk primarily long distance. Amplified handsets and headsets help, but the increased gain from the amplifier also amplifies line noise, so it's often still hard to hear. A "Trunk" is usually a few bucks more per month than a "Line", plus the ordering and installation charge if you are having it changed from a "Line". They will always install new (conditioned) pairs from the CO when changing a line to a trunk.

Guys have asked if there's anything they can put on a line to bring the volume up if it's too low. Unfortunately, there's a problem using an amplifier on a 2 wire full duplex telephone line. On a 2 wire line both transmit and receive are on the same pair, as opposed to a 4 wire circuit where transmit and receive are on their own separate pairs. On a 2 wire circuit, the transmit and receive gets separated in the phone's network, where a hybrid transformer sends receive audio up to your ear (the handset receiver), and sends the transmitted audio back down the phone line to the other end (from the handset transmitter). The hybrid transformer is not 100% efficient, meaning it's can't totally separate the transmit from receive. Maybe it's 90% efficient, which means that 10% of the receive audio gets sent back down the line - basically "feedback." When you amplify the line, that feedback is also amplified, which ends up sounding like ringing, singing or a squealing on the line. Sometimes you just can't amplify a 2 wire line enough to make a customer happy, before it starts to squeal.

On a 4 wire circuit, the transmit and receive have their own pairs. That means you can amplify the transmit and receive separately. There's nothing in the circuit feeding back part of the audio, so there's no squealing. Turn up the gain as much as needed. All of the trunks between COs are four wire circuits (either analog or digital), so the audio levels are perfect on calls across the city, or across the country. There can also be problems with a particular phone or system if the hybrid in it isn't designed properly. The less efficient it is, the less you can amplify the line without feedback, and the more echo you have when the phone or system is attached to a digital line (like VoIP). he only 2 wire amplifier I'm aware of still on the market is the Wilcom SB21-K2 Turbo Amp ( , around $250). It's an unbelievable little line powered device, designed for installation by unskilled Phone Company installers. It's made to go into an NI. The biggest drawbacks are that it has no gain control, and limited gain (maybe 9db?). It sets its level automatically when you dial the local 1KC tone (at the CO that pair is connected to), then a quiet termination, and then flip a switch. Even without a manual volume control, you can set it for maximum gain by dialing a 1KC tone in some other city which fools it - but you may end up with a squeal if you do that.

You may also be able to find used 2 wire amplifiers, like the Reliance VFR I've used it a few times on OPXs, although it's time consuming to install. I don't think it's full duplex (it has voice switching). The VFR5050 is on a small card, so you need to buy a card cage with a power supply. I think it works in those card cages that the Long Distance companies installed for their packs (with 25 pair cables and all), so you might be able to use an abandoned card cage that's lying around (I'm not sure it works). A nice thing about using the correct card cage is that the line gets passed through automatically if the card is pulled, so you don't cut-off anyone if you remove the card (an option?).

THE VOLUME ON CONFERENCE CALLS IS TOO LOW: Lots of guys ask if there's anything they can use to bring the volume up on lines that are conferenced on a phone system, so the outside parties can hear each other. Most phone systems don't have an amplified conference because it's expensive to put the parts in the system to do that. When you simply bridge two lines together, which is what most phone systems do, you lose maybe 7db (the circuit loss on the lines), between each of the outside parties. The person who created the conference in the middle (on the phone system), can hear the outside parties just fine. The two outside parties just can't hear each other. This is the case whether the trunks are conferenced together manually, or the phone system is performing an external call transfer, bridging (conferencing) one trunk to another to forward a call to another premise. If you simply amplified each phone line the same amount in both directions, you'd get feedback or the lines would sound too loud in one direction. The hard part about amplifying a conference call on 2 wire lines is that you only need to amplify the outgoing signal on each line - not both directions. Since an analog hybrid transformer used to separate transmit from receive isn't 100% efficient, you end up getting feedback and squealing when you try to amplify in one direction.

Although there are ways to amplify conference calls using sophisticated analog circuitry along with the most efficient hybrid transformers available, these days it's usually done with a DSP (Digital Signal Processor). The DSP is programmed to digitize the analog call, separate the transmit and receive digitally, digitally amplify the signal in one direction, and then convert the digital signals back to analog. Very few phone systems have amplified conferencing built-in, but that may change as DSPs (and programmers in India or wherever) get less expensive. There's NOTHING that will work to increase the level of conferenced trunks on a phone system except a Conference Bridge. A Conference Bridge is a fairly expensive digital device (with DSPs to adjust the incoming and outgoing volume) that goes on analog station ports on a phone system. To create the conference, you dial into the conference bridge, and manually dial codes to setup or tear-down the conference. Because the DSPs in the conference bridge are programmed to bring the levels up to the correct levels, conferenced calls will sound great.

I personally ALWAYS order 3-Way Calling from the CO for my customers... and they LOVE IT! That heads off the complaints I'd invariably get when they try to make their first conference call using the phone system's conference feature. You just have to make sure you order 3-Way from the phone company, and that you program a flash button on every phone. That's all it takes to have perfect conference calls. Why are they perfect? Because the amplification is applied as needed at the CO on 4 wire circuits, before the line is converted to 2 wire to go to the premise. No amplification has to be done on 2 wire circuits.

WHAT IF THE VOLUME ON A LINE IS TOO LOUD? Touch tones and echo are two reasons that you may have to reduce the volume level of a line. Reducing the level is easier than amplifying it! An Attenuator will reduce the audio level on a line by a set amount, and also reduce the loop current by about 1ma for every 1db of attenuation. If you have DTMF recognition problems, or there's too much echo either on a trunk or analog station port on a digital system, or a system using VoIP lines, reducing the level of the line or port can fix or improve the symptoms. If the phone system doesn't have an option to reduce the level through programming, using physical Attenuators (or resistors) is the only way to get the level down.

Longitudinal Imbalance (AC Voltage):
When you've tried EVERYTHING else... Telephone companies have been dealing with AC on phone lines since they first started serving the same customers as the electric company, locating their lines on the same poles as the electric wires. Since phone lines are often built along the same route as power lines, varying amounts of AC voltage are easily induced onto the phone lines. This AC voltage usually can't be heard, since it's traveling on balanced phone lines (where both sides of the line are exactly the same distance from the central office), called "common mode." The same amount of AC is on the tip as the ring, so you don't hear it in your Butt-set. AC voltage can go as high as 50V before the phone company (in most states) has to do something to bring the voltage down - mainly for safety reasons (touching 50VAC with a sweaty arm could hurt!). The farther a pair for a phone line travels parallel to a power line, whether it's on poles or underground (or buried in the same trench to a gate), the more AC will be induced onto the phone line. The more current that's being used on the power cable, the more AC will be induced onto a phone line running parallel to the power cable. Induced AC voltage will be present on all of the lines in a cable. Whether you hear it depends upon the balance of the line. An unbalanced line will convert the induced AC to metallic voltage and current, which you hear as hum, buzz, crackling, etc.

If a phone line has AC on it, and it's perfectly balanced, you won't hear the AC on your Butt-set. When you connect a phone system or other electronic device that has a reference to ground (and is slightly unbalanced) to that same line, you'll start to hear hum. When you do hear hum on the line, you are usually hearing a harmonic (multiple) of the original 60 cycles, since 60 cycles is too low to be heard on the telephone line. The phone company has a number of solutions available to them when they have too much AC on a line with hum. They usually install a big inductor or choke (a really big and heavy transformer, sometimes called a "humbucker"). In the past, the only thing hanging off the phone line at the subscriber end was a single line phone or an electromechanical PBX that had simple relays that clunked open or closed. Noise and voltage problems had little effect on their operation. AC voltages of 5 or 50 volts didn't bother them much. Modern phone systems use electronic components on the trunk cards. Some of these components cause a small imbalance on the line. This imbalance may not even cause a hum, but if there is a lot of AC voltage on the line, some AC potential is created. Now you've got this AC voltage traveling between the tip and ring, which is something that the electronic PBX or Key System may not be designed to deal with. This 5 or 20 VAC can have adverse effects on the system, like lines that won't ring, false ringing, lock-ups, cut-offs, Caller ID problems, and who knows what. Even if the line is perfectly balanced, the electronics on the trunk cards can be stressed by the induced AC voltage on the line all the time.

Since the AC voltage on the line would be different at each premise having problems, the symptoms may be different even though the premises have the same exact system. A common symptom of high induced AC on a phone line is when Caller ID is intermittent or doesn't work at all, but a cheap battery operated Caller ID box works fine. The battery operated Caller ID box has no reference to ground, so the induced AC stays common mode - exactly the same on the tip as the ring, and Caller ID works fine. When the phone system trunk port is connected, it's not perfectly balanced so there's now more AC or the tip or ring than the engineer designed the system to work at, and Caller ID might not work. The engineers in third world countries who design modern phone systems don't even check to see if induced AC will cause a problem. The problems occur at comparatively few places, so today's phone system manufacturers don't want to put any money into making sure it's not a problem with their system (in other words, they don't know and they don't care).

One of the factors that makes it tough to troubleshoot AC problems is that the AC that's induced onto the line may be different at different times of the day. If there's a big factory on the power line before or after it gets to the subscriber, and the phone line is running along the same route as the power line, you may see a large increase in the induced AC voltage when the factory is at peak operation (using peak power). Maybe the factory uses the most power in the morning, or the afternoon. That means that you may see strange intermittent problems at only certain times of the day. This is the worst kind of problem to troubleshoot, but if you know about induced AC and longitudinal imbalance you at least have some chance of fixing it. If you don't know about it, you're in trouble. You'll usually hear hum on the trunk when you have a longitudinal imbalance, but not all the time. The first step is to take a reading of the AC on the line by measuring from tip to ground, then ring to ground with an AC voltmeter. Because the phone equipment may have a center tapped transformer which could screw up your readings, you should open the line before taking your readings. When I measured our lines, they had about .5VAC (half a volt) from tip or ring to ground. I got the same voltage on both sides of the line. I measured it first on an idle line, and it read the same with the pair closed down and also when I went off hook.

Note that some meters just won't read AC on a telephone line correctly, and there's no way to know whether a particular meter make/model will or won't until you try it. Most Fluke meters will work, but even expensive True RMS meters might not. Since you're measuring AC riding on-top of the DC talk battery, some cheap meters get confused. As soon as you put a meter like this on a phone line, on the AC scale, the readings will just hunt all over the place, never stopping, and never making any sense. We tried lots of meters, and we finally chose one to sell to phone men that works. If you have a telephone company type line tester, you can take a reading of the Circuit Noise and Power Influence. Personally, I've never used these being an Interconnect phone man. If I hear hum on the line at the demarc with the equipment disconnected, I just call the phone company and let them fix the problem out in the field. You should never hear hum or noise on a phone line at the demarc with the equipment disconnected, no matter what the phone company says! Phone company guys use the Noise and Power Influence tests to tell them that there's a problem, and when they've fixed it. You may be able to use it just to give you a general idea of whether there is a problem on the line. There should be "green" areas on these types of meters, indicating the good range. Our lines had 47dbrnC on the Power Influence scale, and 1 to 2 dbrnC on the Circuit Noise scale - both in the "green" area.

The only real way to tell if a longitudinal imbalance is causing problems on your phone system if you read over .5VAC is to put a device which isolates the AC voltage in front of the equipment, to see if the problem clears. There are two types of transformers that can help. The first is a choke, which uses the windings on a transformer to prevent AC voltage from getting to the phone system. The other is a drain, which drains the AC to ground. You may even need a combination of the two. According to the experts at SNC, about the only manufacturer of this kind of noise reduction equipment in the country, the only way to diagnose this is to put one of these devices on the line...to see if the trouble clears. SNC has a gizmo they call the SNIX, which combines both the choke and drain in one case. They also have a tester called the Little Zapper which has a SNIX inside, that allows you to hook up the choke, drain or both using butt-set cords and clips. Once you determine that the hum is gone or the intermittent problems have stopped, you can put a choke, drain or SNIX (choke and drain combination) on the line. SNC's number is , and they have engineers available to discuss your problem.

Longitudinal imbalance can occur after the NI too. I talked to a guy who ran some OPXs from a PBX over to a Merlin system, over 500 feet away. The Merlin system had some CO lines coming into it directly from the phone company, from a different direction than the PBX. Those lines worked perfectly, and were hum free. The OPXs all had hum. As a matter of fact, when he swung an actual CO line into the Merlin using the same house pairs he also had hum. If he used a 500 set or a butt-set, no hum. There was only hum when the line on the house pair was in the Merlin. Obviously, the Merlin had a slight imbalance which allowed the AC voltage that was picked up on the house pairs running through the plant to be heard as hum. This is the perfect scenario for using the Little Zapper to troubleshoot the problem.

Ring Voltage In the old days (a few years ago?), we primarily dealt with ringing from real phone lines. Sometimes we'd have to deal with a channel bank or station port on a phone system, but ringing wasn't much of a problem. The ring voltage was pretty similar, and most of us never had to worry about or measure it. In general, ringing coming from every real phone company Central Office looks pretty much the same (but true rural phone companies can do whatever they need to). It's around 90VAC at 20 cycles per second, with a true sine wave, at about 5 REN. Ringing coming from "fake" phone lines can look very different from manufacturer to manufacturer, or even from model to model. Channel banks, VoIP gizmos, cable company phone gizmos, and analog station ports on phone systems all ring, but there's no way to know how a particular engineer decided to make it ring.

Ring Voltage REN - Ringer Equivalence Number It refers to the load rating of a single old mechanical bell phone. You know - the standard Ma Bell that many of us older than 30 grew up with. The resistance (or impedance) of those ringers is approx 7kohm at the ringing frequency of 20Hz. The "bell" is tuned to resonate at 20Hz. A 5 REN load implies that 5 Ma Bell phones can be placed in parallel and still be rung. The resulting load of 5 REN is 1.4kohm. Therefore a 5 REN port is capable of driving loads as heavy as 1.4 kohm - bottom line. There is also a bell, which represents a similar load with a slightly different electrical model, but it's basically the same thing. Most phones reference the bell on the bottom of the handset (typ 0.2B). 5 phones with 0.2B approximate 1 REN and so on.

Ring Voltage Because these devices only give you "fake" dial tone, the manufacturers don't have to follow any standards or regulations. Today's inexperienced engineers are told to do it the fastest, easiest and cheapest way possible. Often the engineers designing this stuff have never even used a real phone line - they might have a simulator and a couple of books. If every piece of phone equipment looked the same, that wouldn't be a problem. The reality is that different makes and models of phone equipment look very different today. Because most of the phone equipment sold in the US today is made in China or Europe, very little looks like the old equipment we used - even three years ago. A lot of the phone systems and phone equipment used in the US actually is made for European standards - which although similar, are different enough to cause big headaches for telephone men trying to hook this stuff up here in the US. In Europe, 60VAC ring voltage is common, so in many cases US phone equipment connected to phone system station ports that were designed in Europe just don't work well (because they're looking for a minimum 75VAC ringing).

Ring Voltage In the old days (in the US) ringing was 2 seconds on, and 4 seconds off. Then distinctive ringing from the phone company became commonplace, which offered shorter rings. PBX station ports have often had shorter rings, with different ring cadences indicating an inside or outside call. The ring cadence is also different in Europe. There's a possibility that the station equipment you're installing won't recognize a distinctive (or short) ring. Your assignment, should you decide to get paid, is to figure out why the stuff doesn't work - and fix it. The easiest thing to fix is ringing that's too short for the telephone equipment to recognize. A common fax switch usually puts out the standard 2 seconds on / 4 seconds off ringing, as long as it recognizes the ring. There's a pretty good chance that sticking a fax switch between the line with the short ring cadence and the telephone equipment will fix the problem, but it will likely delay ringing for one or two rings, and will probably eat the Caller ID signal - which normally comes between the first and second ring here in the US. It's an easy thing to try to get you going in the right direction.

Ring Voltage AC (Alternating Current), which is used for ringing, means the voltage goes positive, to zero, and then negative by the same amount over a given period of time (for a phone line ringing at 20 cycles, there are 20 complete cycles per second). If it's a sine wave, the voltage tapers from positive to negative, making a waveform that looks rounded at the tops and bottoms (see the chart below). If it's a square wave (which is cheaper to make electronically), the voltage goes straight up to the maximum positive voltage, stays at that voltage for the duration of that part of the cycle, and then goes straight down to the maximum negative voltage (see chart below). On a square wave, the line going from positive to negative is usually vertical, as opposed to sloping on a sine wave. Some real bells (ringers) have a problem with square waves, so some manufacturers shape the waves into trapezoids (with extra electronic components) to improve how their device works with real bells, and to reduce some of the noise that can be generated by using a square wave (see the chart below). Most electronic ringers work fine with a square wave.

Ring Voltage The reading you get with a particular meter on ring voltage depends on the waveform type. See the chart below. It's unlikely that any two of us will get the same reading measuring the same ring from the same source, since we all carry different makes and models of meters. That makes tech support pretty difficult, and makes it important that you use your meter to take readings at lots of customers where you're not having a problem - so you have a good feeling about what's normal and what's not. It's impossible to use your meter for the first time where you're having a problem (to make a diagnosis), since you'll have no basis of comparison. Even worse is that many modern meters, even expensive True RMS meters, won't read AC voltage on a DC telephone line. I guess the inexperienced engineers who designed this stuff just never had to work with phone lines, or measure AC hum on a DC power supply? When you try to measure AC on a phone line using one of these screwed up meters, the display will hunt all over - like from 30 to 100 to 60 to 200 to 100 to 80, etc. If your meter hunts when you put it on the AC scale on a phone line, you need to get a different meter. Since you can't test a meter before you buy it, that's sometimes hard to do!

Ring Voltage A phone man has to be able to measure AC on phone lines these days! Besides ring voltage, a phone man has to be able to measure the induced AC on a phone line. When the AC, measured from tip to ground or ring to ground is over .5VAC, strange things start to happen on phone systems and devices that have a reference to ground (AC powered). Battery operated devices with no reference to ground are usually not effected by AC on the phone line. If your meter starts hunting as soon as you put it on a phone line on the AC scale, you won't be able to check for induced AC or ring voltage

Ring Voltage Looking at the above chart convinced me that taking AC ring voltage readings can be a real problem. Some phone equipment won't respond to a 60VAC ring. Some won't respond to a 40VAC ring. Since any two models of meter could read a 10VAC or more difference, that makes troubleshooting pretty hard! If you already have a meter that works, your best bet is to use it to take readings on many different CO lines, VoIP lines, cable lines, and analog station ports, as you come across them. Make yourself a little chart with all the readings. When you come across a ringing problem, you'll be able to compare the readings on other systems to the one you're having the problem with, as a sanity check. If you use the meter for the first time at the premise where you have a problem, you have no basis for comparison and you really can't trust the readings your getting (and the readings aren't particularly useful to a tech support guy, unless he's familiar with that particular model of meter on that particular type of phone system). A very good technical explanation for variances in AC voltage measurements was put out by Agilent (formerly HP), who makes their own meters ranging from handhelds to lab equipment. I was amazed to read that meter manufacturers calculate True RMS by reading the heat produced by the AC voltage (4 page PDF file):

Ring Voltage Voltage and wave form is only half the equation in dealing with ringing problems. The amount of current that the phone equipment uses, and the amount supplied by the line (or equipment supplying the ringing) can also cause problems. Since most people would have a hard time measuring AC ringing current with a meter, the phone company came up with the REN (Ringer Equivalence Number). 1 REN is the amount of AC current that's used by an old Bell type 2500 set with mechanical bells. The phone company has traditionally supplied about 5 REN from the CO - enough to ring 5 of the old fashioned phones. Since AC ringing current is limited at the CO, if you put 6 REN worth of phones on the line the ringing will either stop on all of the phones, one or more phones will sound very weak, or some phones will ring and some won't. If you have a meter that will read AC current on a phone line (AC ma), you can use an old 2500 set, which uses 1 REN of current, to measure how much current it takes to ring the bell on that set on your meter. Once you know how many ma of current it takes for 1 REN, you'll be set to figure out how many REN a particular phone takes, or how many REN a phone line provides (before it stops ringing).

Ring Voltage Using an analog port on a PBX in our office, we used the Network Meter™ to measure the current it took to ring an old AT&T 2500 set. It took 8.75ma AC. Then we measured the current it took to ring a Chinese phone we sell. It measured 8.26ma AC, but the phone said 1.4 REN on the label (if it was really 1.4 REN, it should have read 12.25ma AC). I guess I'll believe the meter, and figure that each of these phones is really a little less than 1 REN. We then kept bridging more Chinese phones to the PBX analog station port. It stopped ringing when we plugged in the fourth phone, which means that particular station port provides around 3 REN of ringing. When you put 4 REN on the port, the electronics in the PBX shuts down the ringing. The same thing would happen on a POTS line form the Phone Company, at about 5 REN. Now, picture switching from the real phone company to a VoIP or cable phone company, where the ringing comes out of a box connected to the Internet or TV cable. Some of those boxes supply 5 REN, but some of them supply only 1 or 2 REN. That means that although the phones all rang well from the phone company before, they'll stop ringing when the ringing is coming from the VoIP device if it supplies less than 5 REN (unless you unplug some phones?). You'll find specific instructions on measuring REN yourself a little farther down the page.

Ring Voltage The REN number is printed on the bottom of most phones, but newer products might show the REN number inside the FCC registration number. In the registration number US:AAAAAnnBXXXXX, nn is the REN times 10. Just think of it as n.n REN. If the registration number is US:1X23T07A12345, the REN is 0.7. In the new style FCC registration number, there are 5 characters after US, then the 2 digit REN without the decimal point. The letter following the REN is almost always A, B or Z. The REN on telephone equipment can be as low as 0.0 REN (it uses almost no ringing current), or sometimes as high as 2 or 3 REN (usually older equipment). If the phones don't ring properly, add up the REN numbers on the bottom of everything plugged into the line, and make sure it's less than 5. The problem is that if it's not a real phone line, you probably have no way of knowing how many REN the device puts out, unless you measure it yourself. Some VoIP and cable devices put out 5 REN of ringing, but most put out less. Unplug the phones, one at a time, until the ringing starts to work. Few (if any?) analog station ports on phone systems put out 5 REN.

Ring Voltage So how many REN will a particular device that provides ringing provide? If it doesn't say in the manual or on the box, you'll have to call tech support (which could be very frustrating if it's a VoIP or cable company!), or calculate it yourself. One thing to be aware of is that the more REN (ringers) are on the line, the lower the voltage is going to be when you read it with your meter. The readings on the above chart were taken with phones totaling 1.4b REN on the line. The voltages would be higher in all cases with no telephone equipment connected to the line - just the meter. With 5 REN worth of phones connected, the voltages would be quite a bit lower. If you're going to take readings, it would be best to compare apples to apples, and disconnect the inside wiring when you measure ring voltage. If you're close to a CO or SLC, the AC ringing current can be higher than normal, just like the DC loop current. The phone company wants to make sure the pairs will work as far away from the CO or SLC as possible, so they leave everything cranked up. They usually won't adjust it down if you ask them, since there's no procedure to adjust it back up when that subscriber cancels and the line card is used for a different subscriber (who may be farther away from the CO).

Ring Voltage Like high loop current, high ringing current can damage components on a CO line card (usually through heat). If a premise is near the CO or SLC, it's likely to have both high DC loop current and high AC ringing current. Our Loop Current Regulator™ reduces both the DC loop current and AC ringing current, so it's definitely something that needs to be installed if the loop current is high (some NT CO Line cards have a problem with trunks burning out and going low volume if there is high ringing current onthe line). You could reduce the AC ringing current getting to a phone system by putting maybe four 2500 sets bridged onto the line with the phone system. The bells in the phones will use some of the current that would otherwise go into the CO line card and damage the components. That still leaves you with high DC loop current, which will also damage the CO line card, so a Loop Current Regulator™ makes more sense than screwing around bridging phones to the line. Measuring the REN of all the phones on the line, or the available REN on the line, yourself... You measure how many REN worth of phones are on a particular phone line with a digital meter that reads AC current (ma). Just find an old real ITT or AT&T 2500 set with a double gong ringer. The oldest phones won't have a REN number on them, but the old double gong ringers are the gold standard that created the REN measurement. One double gong ringer is 1 REN.

2500 Set Markings (Usually no REN value listed)
Ring Voltage 2500 set from 1973 2500 Set Markings (Usually no REN value listed) AT&T or ITT 2500 Set Double Gong Ringer

Ring Voltage Put the old phone on a real phone line (don't use a station port or VoIP ATA since it might not put out enough current to ring one phone). Put your meter on the AC ma scale (not DC). Your meter may have a different banana jack for the red lead to measure milliamps, or maybe just for AC milliamps. Be sure to look at the designations on the meter's jacks! Put the meter leads in-series with either the tip or ring going to the phone. It must be in-series, not in parallel (which will short the line) to measure the current traveling to the phone. If you put the meter in-series with the tip, the current will come out the tip side of the phone line, in and out through the meter leads to the tip connected to the phone, through the phone and back to the ring side of the phone line. Call the phone line, and you'll see the current it takes to ring the old 1 REN phone (attached in-series after the meter) displayed on your meter.

Ring Voltage The reading you see will be the amount of current your meter reads for 1 REN. Record that number, because that's going to be the current for 1 REN that you're going to use to calculate the REN of phones attached to a phone line, or how many REN the phone line is capable of supporting. To measure the REN of all the phones on a phone line, connect your meter in-series with all the phones, ring into the line and observe the ma reading on your meter. The more phones that are attached after the meter, the more ma (current) you'll see. When you get the reading for all the phones, divide it by the reference number you recorded for 1 REN. That's how many REN the phones are using on that phone line (like 20ma divided by 8.2ma = 2.43 REN) Your meter may show 8.75ma AC with an old 2500 set. If you put four 1 REN phones on the line and they all still rang, your meter would show 35.0 ma.

Ring Voltage When you add the fifth phone, the ringing may stop on all the phones because ring current is regulated at about 5 REN from the phone company. When you draw too much ringing current, you'll see the current drop back down ("fold back") to maybe 10ma - in which case none of the phones will ring because there's not enough current. Adding a load (like one phone at a time) and measuring the amount of current the phones are drawing after you add each phone is the only way to measure the available ringing current on a phone line or station port. You can't measure the available REN on a phone line or station port by simply putting the meter's leads on the tip and ring while the line is ringing, since the meter will short the line and answer it as soon as you put it on the line. The only way to measure available REN is to know what your meter reads for 1 REN (above), then continue to add phones until the ring current folds back - and the phones stop ringing.

Ring Voltage Adjusting an old 2500 set ringer to ring on lower voltages... The old 2500 sets with double gong ringers, and 2554 sets (wall phones) with single gong ringers, have a small bias spring to adjust the clapper on the bell. The bias spring was normally shipped in the high position so the bell wouldn't tap when a rotary phone was dialed or another phone went on and off-hook - which can put out a spike that's enough to move the clapper a little. If you have less than the standard 90V AC ringing and would like to make an old style phone ring, you could try setting the bias spring to the low position to see if it rings.

Bias Spring in Low Position Bias Spring in High Position
Ring Voltage Bias Spring in Low Position Bias Spring in High Position

Ring Voltage Modern phones with real bell ringers probably don't have a bias spring. The Chinese do a good job copying stuff, but I'm pretty sure they had no idea what that wire was for... so they never designed it into the cheap phones they make. Too bad, since most of the stuff they make has pretty crummy ring voltage. If you look inside most modern meters, there's almost nothing in them. Besides the fact that all of the components are surface mount (which are very small), the bulk of the features are controlled by an ASIC (Application Specific Integrated Circuit), which is a microprocessor with everything pre-programmed, and then stuck on the board... they don't buy an off-the-shelf microprocessor from a company and burn their program into it. An ASIC usually looks like a blob of black glue stuck to the board, which is protecting the actual microprocessor and memory (you see a similar thing in one of those greeting cards that plays music).

Ring Voltage A lot of guys wonder why the phone company uses 90VAC at 20 cycles, and the power company uses 120VAC at 60 cycles? Why doesn't the phone company use 120V at 60 cycles? Well, phones became popular before the power companies used AC voltage. Edison's first power plants were DC, not AC. Eventually Edison's competition forced him to use AC, which turned out to be much easier, cheaper and safer to distribute in towns than DC. The original phones used a crank on the side which ran a small magneto to send the ringing signal to the other end of the line (normally the phone company's switchboard). 90 Volts AC at 20 cycles were reasonable numbers considering that a human had to spin the crank by hand, and the bell was a big clapper that had to swing up and back to hit two gongs (if it went too fast, you'd get a clapping or buzzing rather than a ringing sound). Switchboards often used "drops" in addition to a bell or buzzer, which were little spring loaded doors that were released by the ring voltage sent from the magneto on the calling phone. Later switchboards had lights next to the jack for each subscriber, instead of the mechanical drop.

Echo Elimination & DTMF Problem
While echo problems were few and far between in the past, eliminating echo has become a challenge when installing today's VoIP phone systems. What's the quickest way to eliminate echo on a VoIP phone system? Make sure that all of the lines connected to the systemare digital, delivered on a T1 or PRI That's easier said than done, since there are so many analog phone lines out there. T1s are sometimes more expensive for both the monthly service, and the card to connect the T1 to the phone system. T1s are usually more difficult to get repaired, and if a single T1 goes out it could effect up to 24 lines - leaving the customer with no telephone service (even with a T1, it's a good idea to keep a few POTS lines). Digital lines probably won't stop the echo if it was created on the far end of the call or at the phone company itself. If you have a T1 you know the echo won't be coming from the interface between the phone system and the phone lines. A T1 may help echo created on the far end of the call, if the T1 provider runs all of the calls through an echo canceller in their CO.

It's usually not economical for a customer with less than 10 lines to get a T1, but it may be necessary to eliminate echo if it can't be fixed any other way. Some CLECs are offering fractional T1s with only six lines at a reasonable price, but it might be expensive or impossible to get a T1 card for a particular small phone system. It's worth doing a little troubleshooting to see if you can get rid of the echo. If you only spend $20 or $50 a line to get rid of the echo once (instead of a monthly cost), that's probably a lot cheaper than going to a T1. The echo I'm talking about in this bulletin is from the connection between the phone system and an analog phone line, or an analog station port and the phone system. If you have echo on an intercom call between VoIP phones on the system, or only when using a speakerphone or a particular type of VoIP phone, you'll have to figure that out with the phone and/or system manufacturer. Don't confuse an Internet T1 with VoIP phone lines, with a Channelized Voice T1 or PRI. If the customer gets VoIP lines from their connection to the Internet, that may fix the original echo problem - but the overall quality of the call will suffer because the voice packets will be routed over the Internet in a way that may result in garbled voice and echo (there's no way to control the path of the individual packets making up a conversation on the public Internet).

If a digital VoIP phone line is delivered from a private network (so the voice packets don't actually travel over the public Internet), the voice quality should be great. There should be no echo caused by the VoIP phone system itself if it's connected through a T1 or Ethernet connection. In some cases, a LEC or CLEC brings a T1 into the building, but because the phone system doesn't have a T1 card (it only has analog trunk ports), a Channel Bank is used to convert the T1 to up to 24 analog phone lines. Actually, they kind of look like analog phones lines, but most channel banks don't do a great job of emulating a real phone line. If the channel bank is connected to a VoIP phone system you can have echo or other problems, just like from a POTS line. Echo might actually be worse with a channel bank, since there are two 2 to 4 wire conversions using hybrid transformers instead of one on a regular POTS line (on a POTS line the conversion from the 4 wire digital CO to the two wires going to the premise is done at the CO).

Ten years ago a customer with a T1 was given a high priority by most LECs and CLECs. Problems were fixed within hours. Today, there are so many customers with T1s that a T1 is now a commodity, with a service level to match. If it's totally down it can usually be diagnosed and repaired quickly, but because of a lack of training and equipment at the LECs and CLECs, more esoteric or intermittent problems may be impossible to fix (and there's a lot of finger pointing from all parties). Fixing an echo problem by switching from POTS lines to a T1 may be like jumping out of the frying pan into the fire, but you might not have a choice. One other thing that can cause echo and other problems is connecting a VoIP phone system designed for foreign (from other countries) POTS lines to US POTS lines (or vice versa). While a 2500 set will probably be usable anywhere in the world, there are enough differences in phone lines between the US and other countries that there could be echo, volume and ringing problems when you use a phone system on the "wrong lines." If a customer wants you to hook up his Bulgarian phone system to a POTS line here in the US, it might not be pretty.

Interfacing analog lines (or telephones) with VoIP phone systems Remember... If fixing echo was easy, anybody could do it! The hardest cases of trouble are when the echo is intermittent. That's usually because the phone company uses echo cancellers on some phone calls, but not on others. Some COs may be equipped with echo cancellers for long distance calls, but not for local calls. You have no control over whether the CO uses echo cancellers or not. If you have echo or DTMF problems only from certain COs or cities, that may be the reason. You have absolutely no control of where the incoming calls come from, where outgoing calls go to, or whether incoming calls are originating on a VoIP phone line or system. Some of the echo is coming from the other end, and you won't be able to fix it.

The easiest echo to fix is: Echo that you or the person at the other end of the call always hears on a VoIP phone system when you're talking on an analog line or trunk Echo that you or the person at the other end of the call always hears on a regular phone system connected to a VoIP phone line (adapter), and where you don't hear the echo when you connect your butt-set directly on the line (with the phone system disconnected). You've got a 99% chance of getting rid of those types of echo by correcting the impedance of the line using an Echo Stopper™ Adjustable Line Impedance Matcher. If you can hear echo on a 2500 set or your butt-set right on the line all the time, it's probably impossible for you to fix it by doing something yourself at the premise. That's because echo you can fix is usually caused by the delay in packetizing analog audio into IP packets, and there's no delay created by a butt-set. It's possible to fix echo coming from a VoIP adapter if you hear it on a butt-set by correcting the impedance, but less likely.

VoIP phone systems have echo cancellers built-in. Some work better than others. Even the best echo cancellers can't eliminate all echo, but if you correct an impedance mismatch it probably won't swamp the echo canceller in the phone system. Sometimes it takes a second or two for the built-in echo canceller to figure out how to get rid of the echo - it's training itself for that call. If you only hear echo for the first second or two, you may be able to get rid of that echo by correcting the impedance with an Echo Stopper™. By correcting the impedance the system's built-in echo canceller doesn't have to do as much work, so it may be able to train itself in a fraction of a second, rather than a second or two. When you sell a new VoIP phone system, there's no way to anticipate if you'll have echo problems with POTS lines. When a phone system is connected to a digital line like a T1, the interface is very exact - adhering to technical specifications, and there's no analog to digital conversion on the trunks (but there may be a TDM to packet conversion in the system). When you connect a POTS line to the system, the specifications of that phone line are so loose that what you get from either the LEC or CLEC is just a crapshoot. The interface for a T1 line doesn't change depending on the distance from the CO (and there's a single clock that keeps everything in sync), but a POTS line looks a lot different depending on the distance from the CO, the type of CO, and how the line is conditioned by the phone company. Nobody can guess how well it will work until you get it hooked up to a VoIP phone system.

Taking a demo system out to a prospective customer is a good idea if the lines are already in when you're proposing the job. If there are analog stations or OPXs involved in the proposal, make sure you go as far as you can in setting up the system like the customer would be using it - including swinging the OPX over to an analog port on the demo system to make a few test calls. If you hear echo, try an Echo Stopper™ to see if it will eliminate it. If the OPX doesn't ring the far end and/or it won't work at all. The analog station ports on most modern phone systems and VoIP gizmos have lower loop current and lower ring voltage and talk battery than in the past. POTS lines usually work OK on an old 2500 set or your butt-set, but it's a whole different thing hooking it to a VoIP phone system. When you have a problem with a POTS line and report it to the phone company, they make a single phone call from their butt-set and if it sounds OK, they'll close the ticket NTF. They don't care if it doesn't work with your customer's equipment, even though in the real world nobody has used a 2500 set in a business for years.

The source of echo problems on modern phone systems is often the trunk, where a regular analog two wire telephone line interfaces with the digital phone system - which is "four wire," with separate transmit and receive paths inside the system. You skip the four wire to two wire conversion when you connect a T1 to the phone system, since both the T1 and the phone system use separate transmit and receive (four wires). There's a transformer inside every analog telephone or CO trunk card who's purpose is to separate transmit and receive. It's called a hybrid transformer. The hybrid has two wires that connect to the trunk, and on the other side of the transformer are four wires - a pair for receive (going to the receiver in the handset in a standard phone), and a pair for transmit (going to the mic in the handset on a standard phone). That hybrid is the source of most echo problems that you can fix. The hybrid is basically two transformers wound around a core, or an electronic version of that. Some hybrids are better than others. What makes them better? They're more efficient, meaning that there is less "leakage" between transmit and receive, or reflected back out the two wire side. On a regular 2500 set, the hybrid in the network purposely sends some of the transmitted signal from the mic to the receiver, which is called sidetone. The hybrid used on a trunk card is much more efficient than a 2500 set because the sidetone isn't needed on a phone system (it's created at the station so the conversation is more natural to the user).

Even though the hybrid on a trunk card is efficient, it's not 100% efficient. Some of the transmitted data "leaks" and gets mixed with the received data, or reflected back to the caller on the 2 wire side. It's at such low volume that the leakage just doesn't matter using an analog or regular digital phone system. The biggest problem with that inefficiency on regular phone systems is that if you try to amplify a two wire telephone line, at some point you'll get squealing due to the feedback from transmit to receive, just like you'd get if a microphone is too close to a speaker on a PA system. The feedback is why you don't see amplifiers for two wire telephone lines, and why you don't see amplified conferences on phone systems - at some point you'll get the squealing, usually before you've amplified it loud enough to hear well. So, you've got feedback on an analog phone or phone system from the inefficient hybrid, but it's never mattered until now because you can't hear it (it's happening at almost the exact same time, so you don't hear it as "echo"). That same hybrid is on the trunk card on digital phone systems we've been using for years, and we've never had an echo problem (until VoIP came along).

A digital phone system takes analog speech and runs it through a codec (Coder-Decoder) that digitizes or "undigitizes" the audio. The codecs on traditional digital TDM phone systems are so fast that there is very little delay, and even though some of the transmitted data is mixed with the received data in the hybrid, the delay is so small that we've never noticed it (but it's there). You'd be hard pressed to hear any difference between a call on an analog phone system and a digital (TDM) phone system. VoIP is a different story... When the Internet was created, it was determined that packets of data would be much more efficient traveling long distances than a single digitized stream of data (like TDM in a digital phone system or on a T1). Packetization means that the web page you're looking at could have gotten to your computer through several paths across the country. Some of the packets may have gone through Florida, and some may have gone through California. The delays for each packet are normally much less than 100ms (a tenth of a second) per segment between routers on the Internet (it may take quite a few segments to get to you). Your computer puts the packets together in the correct order so you see everything in the right place on your screen. If it takes half a second longer to get the top part of the web page than the bottom part, nobody cares.

When people decided to put voice on the Internet, they had to divide the conversation up into packets. That's the only way the public Internet can get data from one place to another. There have been many methods of digitizing voice through the years. Until the Internet it really didn't matter how it was done - the results were essentially the same. Unfortunately, the only way to digitize voice and put it on the Internet is to packetize it for the Internet using IP (Internet Protocol). While these packets work great for data, which can arrive a little late or in the wrong order, the whole concept works badly for voice over the public Internet (but it works OK on a LAN or private WAN). One of the troubles with creating packets for IP is that it takes a while for the codec to do its work - digitizing the voice and putting it in the the packets. It's not a real long time, but it's long enough for us to start hearing that inefficiency in the hybrid because there's a delay. With analog or TDM, there was little or no delay and we just didn't notice the inefficiency as echo, even though it was there. The better the hybrid matches the phone line, the less you'll notice echo on a VoIP phone system. If all phone lines were exactly the same, the hybrid would be as efficient as possible. Because all POTS lines are different in one way or another, the hybrid is never as efficient as it could be.

Echo doesn't just effect voice. While it's annoying to talk on a call with echo, there's a good chance that an automated attendant or voice mail system won't work correctly on calls with echo. The DTMF digits will look pretty strange to the device hearing them. A 60ms DTMF digit followed by 50ms of an echo of that digit can cause recognition problems that are tough to diagnose, especially if the echo is intermittent on incoming calls. In most cases DTMF digits aren't actually transmitted as audio from end to end over the Internet, they're sent as data. The line is split at the far end (the far end doesn't hear that little piece of audio), and the digit is reproduced at the other end of the call - throwing away the actual audio for that digit. The person pushing the DTMF key hears the audio in their ear... but the problem is that some of that tone is sent down the line to the other end as an echo. Echo problems can also occur with analog station ports on a VoIP system, since each port has a hybrid transformer interfacing the analog phone or OPX, and there's a delay involved in the codec that changes the four wire digital (IP) side to the two wire analog side. Even with digital trunks, you may still have echo on calls involving an analog station on a VoIP system. Troubleshooting would be the same as on a POTS line with echo. In some cases, you just won't be able to fix it, but if it's caused by an impedance mismatch, you probably can with the Echo Stopper™.

If it's Near End Echo, users on the phone system won't hear the echo, but the caller on the other end of the call will hear the echo. In that case, you need to call into the system to hear the echo as you're trying to fix it (with echo canceller settings in the system, attenuation, or the Echo Stopper™). Echo problems can also show up only when the user is on a speakerphone, when regular calls on the handset aren't a problem. On VoIP calls, If the transmitter in a phone can hear the audio coming through the receiver, there's a good chance you'll get echo - but if the user is on a handset the receiver is usually sealed against their ear, and the transmitter never hears the received audio (unless the user has a hole in his head?). On a speakerphone, it's very difficult to totally separate the transmit and receive audio, so the design of the speakerphone is important as to whether it will work OK on a VoIP system or VoIP phone line.

Fixing the echo problems... These are the troubleshooting steps to take: STEP 1: Echo cancellers STEP 2: Attenuate (reduce) the volume of the line STEP 3: Impedance problems STEP 4: Loop current problems STEP 5: Order a T1 Remember... If it's Near End Echo, users on the phone system won't hear the echo, but the caller on the other end of the call will hear the echo. In that case, you need to call into the system to hear the echo as you're trying to fix it (with echo canceller settings in the system, attenuation, or the Echo Stopper™).

STEP 1: If you can adjust the echo canceller in the phone system from programming, see if that helps. Setting the echo canceller too high will either do nothing, cause clipping of one or the other party when both people try to talk (kind of a ticking or buzzy sound), or create distortion so that the voices sound unnatural. Even if a previous technician told you that he adjusted the echo cancellers, check it anyway. You can't skip any steps in the troubleshooting process. Assuming anything can cause you to chase your tail for hours or even days. STEP 2: If you can adjust the volume of the phone line (the db level) in the phone system from programming, see if that helps. Since the echo should be pretty far in the background, reducing the volume of the phone line by a couple of db might help. On the other hand, that 2db could be the difference in being able to hear well on a phone call, and having trouble hearing or being heard. Even if you don't leave it that way, try reducing the db level to see if it gets you anywhere. The more you know about your problem, the easier it will be to get it fixed in the long run. The only way to know whether attenuating the line (lowering the level) will help the echo is to put the attenuation in, and see if the echo problem improves (without making it hard to hear).

Not all phone systems have adjustments for the db level in programming, and sometimes reducing the volume on the line before it gets to the hybrid will help even when adjusting the gain in the phone system through programming doesn't (because there's less audio to get reflected back from the inefficient hybrid). Depending on the amount of impedance mismatch, adding attenuation could correct echo in one direction, but make it worse in the other (if the outside party didn't hear echo before, you may have fixed the echo for the phone system user but have made it worse for the outside party - or vice versa). You can reduce the gain using hardware. Use regular 1/2 watt resistors, or db attenuators made for reducing the level of a phone line (which are basically resistors in box with a connector). The pre-made attenuators come in 1, 2, 3, 4, 6 and 8db models. You should never put more than 2db of attenuation in-front of a VoIP system, since more attenuation than 2db could actually make the echo worse in the other direction. Once you determine how much attenuation you need with resistors, you can order the attenuator you need, or just leave resistors on the line.

Note that a db attenuator is not the same thing as a Loop Current Regulator or Attenuator, which is specifically made to reduce the loop current (DC) without lowering the db level of the line (which is AC audio). Loop Current Regulators or Attenuators use capacitors to block the DC while letting the AC audio through to the phone system, so the user won't have problems hearing. For echo, you want to attenuate the AC audio to see if you can get rid of the echo. 66 Block db Attenuator Modular db Attenuator

You can simply put resistors in-series with both the tip and the ring to lower the db level. 100 ohm resistors in-series with the tip and ring will lower the level of the line by about 1db (be sure to use 1/2 watt or bigger resistors, or they could burn up). Putting 220 ohm resistors in-series with the tip and ring will bring the level down by about 2db, and it also reduces the loop current by about 2ma.You can put resistors in-series with each other, like two 100 ohm resistors in-series to make 200 ohms of resistance. You must always keep a telephone line balanced, so whatever you put on the tip side has to be the same as the ring side, or you'll create an imbalance (causing hum and noise). Never put just one resistor on a phone line! Don't let the loop current drop below 23ma. You must measure the loop current while you're trying to attenuate the line to keep it from going below 23ma. I suppose you can use resistors or attenuators without knowing the actual circuit loss (db level) on the line, but you shouldn't go below -7.5db of circuit loss from the CO or it will be hard to hear.

If you want to test it and not guess about how low the circuit loss is, you need the phone number for the thousand cycle tone at the CO, and you need a circuit loss tester. If you don't know the phone number of the 1KC tone at the CO, then you need a 1KC tone generator so you can do a loop around test (send from one line at the premise, and receive on another line). To test circuit loss, you normally send from the CO at 0db, and measure what you get at the premise. It has to be less than 0db since there is always a loss as the audio travels over the copper pair. Generally speaking, anything over -7.5 is OK. Circuit Loss Tester 1KC Tone Generator Putting in 1 or 2db of attenuation temporarily to see if it helps the echo is fine while testing. The more you know about your problem, the better.

Modular 1 to 4db Loss Insertion Tester
Echo Elimination & DTMF Problem Modular 1 to 4db Loss Insertion Tester You can use a Modular Loss Insertion Tester if you don't want to mess with resistors during testing. It lets you put 1, 2, 3 or 4db of loss in a line, depending on the position of the two switches. Putting it in-series with a 4db Modular Attenuator will let you insert 5, 6, 7 or 8db of loss in a line (you'd only put that much loss on a very loud line, at a premise that's very close to the CO), but for VoIP you need to limit the attenuation to 1 or 2db. STEP 3: If you can adjust the impedance of the phone line in the phone system from programming, see if that helps. The choices are usually 600 or 900 ohms. Sometimes there's a jumper or switch on the trunk card to select between 600 and 900 ohms. Sometimes there will be a choice for balanced or terminated. Terminated should be the first choice, but if it doesn't work, try balanced. All you're trying to do with these settings is match the impedance of the hybrid on the trunk card to the impedance of the phone line. If it doesn't tell you the impedance is of the trunks in the manual, and tech support doesn't know, there's no field test equipment that will give you that information. Likewise, it's impossible to know whether the phone line is actually 600 or 900 ohms.

Connecting a 600 ohm phone line to a 900 ohm phone system (or vice versa) usually doesn't matter, but an impedance mismatch can make the hybrid less efficient, causing echo on a VoIP system. The echo effects the conversation, but even more frustrating is the echo from an impedance mismatch that causes DTMF recognition problems (that are difficult to diagnose/repair). Since you can't measure the impedance of the phone line or system, the only way to see if there's an impedance mismatch is to change the impedance to see if the trouble clears. The easiest way to do that is with the Echo Stopper™ Adjustable Impedance Matcher. This is as close to magic as it gets. Echo Stopper™ Adjustable Impedance Matcher

To use the Echo Stopper™ you must be able to reproduce the echo. Call in to the line you're working on from another line, or call out on a system phone to another line. Put the Echo Stopper™ in-series with the phone line, and adjust the black POT on top to see if the echo goes away. If not, push the Red Range Switch, and again adjust the recessed pot. If the echo goes away, you need an Echo Stopper™ on that line because you have an impedance mismatch. If it doesn't help, you don't need it. In the past, we've had a 600 to 900 Ohm Impedance Matcher to help get rid of echo problems, but it wasn't all that effective. We finally figured out that phone lines are seldom exactly 600 or 900 ohms. Likewise a phone system may not be exactly 600 or 900 ohms. When we made the Impedance Matcher adjustable, the echo just magically disappeared when we turned the POT. As you adjust the POT, the impedance changes. On the lines we've tested it on, the POT usually has to be turned quite a bit to get rid of the echo, which demonstrates that we're not dealing with a clean 600 or 900 ohm impedance, but somewhere above or below that. Don't forget to try the Red Range Switch in both positions. Unfortunately, there are more sources of impedance problems that can make the hybrid less efficient, causing echo. In some cases, the solution may be less expensive than an Echo Stopper™...

Sometimes the line isn't terminated at voice frequencies. A quick test is to bridge a 2500 set (on-hook) or your butt-set in monitor position on the line to see if the echo and/or DTMF problems go away. If they do, you can put a 600 ohm resistor in-series with a .47mf capacitor, across the line. If you don't want to mess with a resistor and capacitor, you can get a Half REN Line Terminator. 66 Half REN Terminator Modular Half REN Terminator

Modular Half REN Terminator
Echo Elimination & DTMF Problem Another cause of impedance problems is misplaced load coils. Load coils are inductors that are placed on a phone line at certain intervals to boost the volume of the line. They are absolutely necessary on long loops, or you wouldn't be able to hear. Unfortunately, the plant records (which document where all of these load coils are) are pretty bad. Nobody knows where a lot of the load coils in this country are. If they're on a line where they're not needed, they cause impedance problems. Load coils are normally added to a whole binder in a cable (25 pairs), so when an order for a new line goes to engineering they just pick pairs that are already loaded, if load coils are needed. Sometimes they run out of loaded pairs in a particular direction, and they add load coils just to the pairs being installed. When that customer moves, those pairs are reused - but often the records don't indicate that there are load coils on the pairs, so the new customer gets a pair with load coils that screw up the impedance of the line (because they're not needed). Load coils are normally placed on long loops - about 18,000 feet or more. There are strict guidelines for their placement. If they're put in the wrong place they change the impedance of the line and cause volume, DTMF, or echo problems. The first one has to be 3,000 feet from the CO, and the following load coils are placed at 6,000 foot intervals. There must be 3 or more load coils on the pair. Modular Half REN Terminator 66 Half REN Terminator

So what if there's a stray load coil here or there? For speech on a 2500 set, it won't matter much. For a 56K modem, it will slow it down. It will probably stop an ADSL modem from working. For calls answered by an automated attendant, voice mail, fax server, or anything else that needs to hear DTMF digits - it may make digit recognition flaky. For speech on a VoIP phone system, it causes echo because the impedance of the line isn't correct, which makes the hybrid transformer less efficient. Finding misplaced load coils is very difficult. Trying the Echo Stopper™ will let you adjust the impedance of the phone line to improve the impedance match. Seeing if the echo is fixed by the Echo Stopper™ first makes sense. If you have echo or DTMF problems, and have checked all of the other fixes listed here, ask the phone company for a meet to find out if there are mis-placed load coils. You can ask them (in advance) to bring out a TDR (Time Domain Reflectometer) because you suspect mis-placed load coils, but the guy will likely show up without one. Maybe they'll bring it out on the second meet? Maybe they have one?

The phone man will connect the TDR at the premise, and look back towards the CO. The TDR will give him a graphical representation of every splice, connection and half-tap on the pair, as well as the first load coil. The TDR will show the feet to each squiggle (connection), which the phone man can then walk or drive to. The load coil has a specific squiggle (signature) on the graph. Some TDRs are able to see past the first load coil to see other load coils on the line. The phone man will be able to figure out the length of the pair from the CO, check the records for that line to see if the pair should be loaded, and see whether the load coils that are on the line are where they should be - or if there's one or more that shouldn't be there at all. Dealing with the phone company is probably as hard as it gets, since you're depending on the phone company to confirm your suspicion. The phone companies do OK at fixing a problem if you diagnose it and tell them what's wrong, but they don't do well at finding these kinds of problems themselves.

Riser Bond TDR There are two types of TDRs. The most common type can only see to the first load coil from the premise. Riser Bond sells one that will see all of the load coils on the line. Neither are cheap. Riser Bond is at I don't think you can rent TDRs that will see past the first load coil, but if you just need to see to the first load coil, I think those are available at communications equipment rental companies.

STEP 4: Check the loop current on the line. High loop current will cause the components on the trunk card to run hot. Sometimes hot enough to damage them, and sometimes hot enough to make the components so warm that their value is outside the range that the engineer was expecting when he designed the circuit. Maybe they'll be louder than normal, which would increase the echo? Running the system with high loop current means you're now the first one to test the phone system to see if it works at that high of a loop current. The normal range for loop current is 23 to 35 ma (some telephone equipment doesn't like anything higher than 27ma). Loop Current Tester

Low loop current also causes strange things to happen when the components run out of spec, so it's definitely worth checking the loop current. You can check it with any digital meter that has a range for DC ma. Be sure you set your meter to DC current, be sure you use the correct banana jack (the + lead often goes in a different jack for current than for voltage), and you are connecting the meter in-series with the tip or ring so the electricity is flowing through the meter. You'll read about 0ma (or maybe .01ma) when you're on-hook (hung-up), and the actual loop current when off-hook. You can only go off-hook with one telephone for testing, don't go off-hook with the phone system and your butt-set at the same time or your reading will be meaningless! The Loop Current Tester is easier to use than a meter. Just put it on a line, press the button, and an LED will light indicating a range for the loop current (from LOW to EXTREME). STEP5: That's all you can do. It's time to get a shiny new T1, and hope that fixes it!

It wasn't that long ago that phone men were soldering wires together!
SPLICING WIRES Static on a Phone Line can be Fixed or Prevented! Customers HATE Static! How you Splice a Cable Makes All the Difference Because a telephone line always has DC voltage on it, with AC audio riding on top of it, if there's a bad connection of any kind anywhere along the line you'll hear static. Connections on a phone line have to be perfect! Just twisting two wires together may look like a good connection, but oxidation eventually develops on the surface of the wires where they're touching each other, which adds resistance to the connection. On a telephone line with DC voltage, you'll hear that resistance as static. It wasn't that long ago that phone men were soldering wires together! The first splices to telephone wires were done with a big soldering iron that was heated with a gas torch (it wasn't electric). Big electric Black Beauty Soldering Irons were used on solder frames on PBXs through the 80's. Why did the phone men go through all that effort to solder the wires instead of just twisting them together? Because they had to avoid static, and that was the only way to do it.

SPLICING WIRES Maybe you twisted the wires together on your stereo speakers, and they work fine? There's no static. That's because there's no DC coming out of an amplifier going to speakers. It's strictly AC audio. When the oxidation develops on the speaker wires that you twisted together, the resistance that eventually develops from the oxidation makes the speaker volume sound a little lower - so you just turn up the volume on the stereo. Since there's no DC, there's no static on the speakers. Likewise, you can use wirenuts on 110VAC or speaker lines, but they're eventually going to cause static if you use them on a telephone line. On a telephone line, you can also get static from a short from one or both sides of the line to a foreign voltage or ground. The foreign voltage or ground may be because water has invaded the cable. Water conducts electricity, and is shorting the telephone line to conductors in another pair(s), or to earth. The static may also be caused by a nick in the insulation, shorting the bare copper wire to other conductors or earth (ground).

SPLICING WIRES Intermittent static is often caused by aerial lines that have nicks in the insulation. When they swing in the wind, the bare copper wire shorts to other conductors or pole hardware. These are called Swingers. While you may be able to tape up a wire with a nick in the insulation to prevent it from shorting, in the telephone business it's more common to cut out the bad piece of cable, and splice the ends together, or splice a good piece in if the cable wouldn't be long enough. If it's a buried cable, you need to use gel filled (waterproof) splices, and put the whole splice in a Waterproof Splice Enclosure, which keeps water from getting into the cable from the open ends (where the jacket has been cut). No matter how much tape you use, it won't be enough to prevent water from eventually seeping into that splice! Use a Splice Enclosure. So Why Aren't We Still Soldering Telephone Wires?

Insulation Displacement Connectors
SPLICING WIRES IDC Insulation Displacement Connectors Insulation Displacement Connectors are simply squeezed onto a wire. They have a little slit that cuts into the insulation (displaces it) and slices into the copper wire as it's pushed into it. There are lots of different types of IDC connectors, including the 66 Block, CAT5 and CAT6 jacks, Krone and 110 Blocks, and even regular Modular Plugs. There was actually one type of splice connector that came out before IDC connectors. The Beanie or B-Wire Connector was the splice of choice at all of the phone companies for many years. The Beanie is just a little metal tube that's big enough to stick about three 24 gauge telephone wires into, with a vinyl insulating jacket. The tube has lots of little sharp points in it that slice into the insulation and the wire, creating a GAS TIGHT CONNECTION.

SPLICING WIRES The Gas Tight Connection is the secret of making a good splice. When the metal in the splice is pushed into the wire so tightly that no air can get to where the metals meet, no oxidation can occur - and you'll never get static from that splice. A pin sticking into a copper wire won't give you a Gas Tight Connection. That pin would be sitting on-top of the solid copper wire, and a layer of oxidation would eventually form (unless there was constant hard pressure on the pin). The Gas Tight Connection is formed when the material used in the splice actually slices into the sides of the copper. The pressure created by the small U shaped slot, that the wire is forced into, creates the Gas Tight Connection.

SPLICING WIRES All Telephone Splices and Connecting Blocks Provide Gas Tight Connections If you hear static at the Phone Company demarc, with the pair to the premise open, the Phone Company will have to fix the static. The only way to get rid of static is to repair the bad connection. There are no filters that will get rid of static, since by the time you hear it - it's just audio. If you filter out enough of the audio spectrum to get rid of the static, you'll also get rid of the speech! -WIRE CONNECTORS (BEANIES) - Non-Filled! B-Wire Connector Bag of 500 Plain Beanies Splices up to three 24 Gauge Telephone Wires Together

SPLICING WIRES Don't strip the wires! Just stick the wires into the Beanie, and squeeze it with a Pliers or the heel of a set of Dikes. The inside of the Beanie is full of little sharp points that go right through the insulation when it's squeezed, and slice into the wire, creating a Gas Tight Connection. B-Wire Connectors aren't used by phone companies any more (they use UY and UR connectors), because they couldn't stop phone men from stripping the jacket off the wire before putting it into the Beanie. Stripping the wire isn't bad if it's done with the correct stripper (like the notch in a phone man's scissors, long nose or dikes), but a lot of the phone men just squeezed the wire in the blade of the Dikes, and pulled the insulation off. That creates a little notch in the copper wire where they squeezed the dikes on the wire. Once the notch is in the wire, it's very easy to break the wire right at the notch, after it's moved a few times. That left lots of cases of dead phone lines, just because the phone man didn't do his job properly.

SPLICING WIRES Don't Strip The Wire! B-Wire Connectors are made to be used on solid copper telephone wire, which has a very thin insulation. There's no need to strip the wire, although it won't cause any problems if you strip it properly. You can use B-Wire Connectors on other types of small gauge wire, both solid and stranded, but you'll have to strip the heavier insulation off of those wires because the little teeth in the Beanies won't be long enough to pierce the insulation. I personally like using these better than UY/UR connectors (below). Probably because they're cheaper, and give me a little more flexibility (they take 2 or 3 wires). I have gotten four wires in a Beanie by stripping the insulation, but I don't think it's a good idea. On a historical note, in the old days Beanies were available taped together on reels. The splicer would feed these into a breadbox sized metal box, which used compressed air to crimp the Beanie, when he stuck the wires in and stepped on a foot operated switch. NOTE: Don't smash a B-Wire Connector when you squeeze it! If it's squeezed too hard, it will bend over the sharp points, and they won't slice into the wire correctly. These B-Wire Connectors are PLAIN, not filled with waterproofing gel.

Never just splice, tape, and bury the wire
SPLICING WIRES COAX and TWISTED PAIR SPLICE ENCLOSURE Coax and Twisted Pair Splice Enclosure 6" long X 3/4" diameter. Shipped with Rubber Grommets that seal by compression when the ends (caps) are tightened. Never just splice, tape, and bury the wire Use a SPLICE ENCLOSURE Use a Splice Enclosure to keep water from getting to the individually spliced wires. Tape just doesn't make it! The Splice Enclosure is for a direct burial splice of RG6, RG11, and RG59 coax, and 2 to 4 pair telephone cable. Quick and easy to install. No special tools are required. No mixing of any compounds or messy gels. Re-enterable for visual inspection. Just unscrew the cap that holds the special rubber grommet that seals around the cable. Use Waterproof F-Connectors to splice coax, or Sealant Filled Beanies or UY Connectors to splice twisted pair cable.

SPLICING WIRES UY 2-WIRE CONNECTOR UY Connector (Splice)
Splices two 22 to 24 Gauge Solid Copper Telephone Wires Don't strip the wires! Just stick the wires into the two holes on the UY Connector as far as they will go (you'll be able to see them through the plastic), and squeeze the Yellow top all the way down so it's flat, with a Pliers or UY/UR Crimp Tool (below). That's it! UY and UR Connectors are the splice of choice of all the Phone Companies in the US. UY Connectors are made to be used on solid copper 22 to 24 gauge telephone wire, which has a very thin insulation. Do NOT strip the wires! NOTE: If you strip the wires before inserting them into the UY Connector, it won't be a good splice! UY Connectors are filled with a small amount of waterproofing gel.

SPLICING WIRES UR 3-WIRE CONNECTOR UR Connector (Splice)
Splices two or three 22 to 24 Gauge Solid Copper Telephone Wires Don't strip the wires! Just stick the wires into the holes on the UR Connector as far as they will go (you'll be able to see them through the plastic), and squeeze the Red top all the way down so it's flat, with a Pliers or UY/UR Crimp Tool That's it! There are three holes on the UR Connectors. You can use all three, or just splice two wires together, leaving one empty. UY and UR Connector are the splice of choice of all the Phone Companies in the US. UR Connectors are made to be used on solid copper 22 to 24 gauge telephone wire, which has a very thin insulation. Do NOT strip the wires! NOTE: If you strip the wires before inserting them into the UR Connector, it won't be a good splice! UR Connectors are filled with a small amount of waterproofing gel.

SPLICING WIRES UG 2-WIRE TAP CONNECTOR UG Connector (Tap)
Taps one 22 to 24 Gauge Solid Copper Telephone Wire onto another wire. There's no need to cut the second wire! Don't strip the wires! Just stick the wire that you're tapping off of (that you don't want to cut) into the slot on the side of the UG Connector. Put the new wire into the hole on the UG Connector as far as it will go (you'll be able to see it through the plastic), and squeeze the Green top all the way down so it's flat, with a Pliers or UY/UR Crimp Tool That's it! There is one hole and one slot on the UG Connector. You can use the UG Connector as a splice by putting one cut wire into the slot (so it sticks out past the end of the UG), and the other into the hole. UG Connectors are made to be used on solid copper 22 to 24 gauge telephone wire, which has a very thin insulation. Do NOT strip the wires! NOTE: If you strip the wires before inserting them into the UG Connector, it won't be a good splice! UG Connectors are filled with a small amount of waterproofing gel.

SPLICING WIRES PLIER TYPE UY/UR CRIMP TOOL
Yellow Handled UY/UR Crimp Tool Crimps the top of a UY / UR / UG Connector down just the right amount. Built-in wire cutter. About the same size as a regular Long Nose Pliers.

CAPACITORS FOR PHONE MEN
These capacitors are rated to take the ring voltage on a phone line (90-100VAC). More common 50V capacitors may burn up. Capacitors are used to block DC voltage. The most common use for capacitors in Telephony is in the ringing circuit, where they are always in-series with the ringer or bell. Without a capacitor in series with a bell, when the phone rang the line would be tripped (or would stay off hook all of the time). The capacitor allows the AC ring voltage to pass through to the bell, while blocking the DC voltage which would take the line off-hook. Another common usage for capacitors is getting audio off of a line with talk battery. If you put a line with talk battery into an amplifier or recorder, the DC voltage will probably look like foreign voltage to the device - and it won't sound too hot. Putting a .47 or 1mf cap in-series with one side of the line going to the amp will block the DC and just pass the audio (which is AC). Keep in mind that if the line rings, it may blow up the amp or recorder! Ring voltage is AC, just like audio. You do not have to put capacitors in series with both sides of the line feeding the amp (or whatever), since there is no DC path to become imbalanced (the cap blocks the DC). You wouldn't want to run an audio pair a long distance after the capacitor. Keep some of these in your case! .47mf 100V Capacitor

CAPACITORS FOR FIXING RF PROBLEMS
They must be used in pairs, one on the tip to ground, and one on the ring to ground. These will work well for lower frequencies like AM, but will have little or no effect on FM. Using capacitors to drain the RF to ground can cause other problems on the line, because of increased capacitance. Keep some in your case! .01mf 100V Capacitor

See if these things work before you drop the Phone Company...
Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Broadband If you have ADSL from your Phone Company, you probably need to keep a phone line. Some DSL providers will now put ADSL on a dedicated pair (you don't need a phone line), called Bare ADSL. If your broadband connection isn't reliable, your VoIP phone service won't be reliable. The more bandwidth you have in each direction the better for VoIP. If you can get SDSL (Synchronous DSL), where the speed is the same for both downloading and uploading, that would be good (harder to get, and usually more expensive). A real data T1 would be 1,500K both up and down, which is as good as you can get - but if you fill up that pipe with music or video downloads etc., your calls will still sound bad. Consider getting a separate broadband (DSL or T1) connection just for voice if you're planning to use only VoIP lines. It will save a lot of grief later. Having two totally separate CAT5 networks in your office, one for VoIP and one for data, makes the most sense.

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Bandwidth Bandwidth is the most important component of any VoIP telephone service. We've all heard calls that are garbled or choppy, and it's always because of a bandwidth issue (either on the local network or somewhere on the Internet). With most VoIP providers, you need about 128K for each VoIP telephone line, in both directions. If you have four lines, you need 512K both upload and download. Most ADSL lines are very fast downloading, maybe 1,500K, but they limit the upload speed to maybe 384K. That means that even if you aren't uploading stuff from a PC to the Internet while you're talking, you don't have enough bandwidth to have four people talking at the same time - you'd need at least 512K upload speed. In this case, you'd probably hear the other people OK (with your 1,500K download speed), but they'd have a hard time understanding you (it would sound garbled). On some broadband connections, like Cable, your connection speed will be reduced when a lot of other people in the neighborhood are using their Cable Modems, so your voice calls will sound worse during that time. If you use a computer on the Internet at the same time, things will really get garbled from time to time. If you have a 1,500K T1, and the company selling you the T1 only has two T1s feeding the neighborhood with 20 customers (3,000K), if other users are downloading stuff totaling 2,500K that only leaves 500K of bandwidth for your VoIP calls - even if you're paying for a whole T1. Probably OK at a home, but it doesn't give a good impression at a business.

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Bandwidth You would have the same issues using a Hosted PBX, where you use electronic VoIP telephones with buttons and a display connected to your office Ethernet network. These phones "talk" to a PBX located somewhere else in the city (or world... but closer is always better). A Hosted PBX will give you more features that are easier to use than with a standard single line analog phone, without your having to buy a phone system at all. Problems arise from the fact that all of the signaling and voice packets have to travel through your office, through your ISP (Internet Service Provider), and through the Internet to the Hosted PBX service provider. If you had a direct T1 to your Hosted PBX provider that doesn't use the Internet, the service should be perfect (if the Hosted PBX doesn't go down, and the Hosted PBX service doesn't get their phone lines over the Internet).

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Number Portability It's OK to port a real phone number to the VoIP company (it usually goes through eventually), but you won't be able to take the VoIP phone company's number to another phone company (don't give out any numbers the VoIP provider gives you - ever). Most VoIP providers "rent" the numbers from another company, so the numbers aren't theirs to give you. If a company other than a real phone company or LEC (Local Exchange Carrier) tells you that you can keep their phone number forever, don't believe it. Because most CLECs (Competitive Local Exchange Carriers) and VoIP companies "rent" their numbers from other companies, if the company who actually owns the number decides to exit the business for one reason or another, and the number can't be ported for one reason or another, the number is lost forever - not yours forever. Always get your phone number from a real phone company (LEC or ILEC - Incumbent Local Exchange Carrier), like Verizon, Quest, AT&T, etc. Then port it to the CLEC or VoIP company of choice once it's in and working (the LEC could still take it away from you, but that's very rare). It's also possible that an 800 number could also be taken from you, but again that's rare. Because the 800 number service provider owns the 800 number, not you, it's possible for someone to hijack the 800 number and for you to lose it (by mistake or on purpose).

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Battery Backup None of this stuff works without power, unlike a real phone line. None of it takes a lot of power, so a good sized battery backup from the computer store will probably keep it going for quite a while (if the batteries are good, but most batteries go bad within a couple of years - and you find out during a power failure).

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Alarm System It probably won't work on a VoIP line without some changes. Although some VoIP providers tell you to simply plug their VoIP device into the nearest jack - after disconnecting the Phone Company's line where it comes into the building, the alarm won't work that way. Coordinate VoIP with your alarm company. The reason the alarm won't work is that the alarm is using tones to communicate, like a modem or sometimes like a touchtone phone. VoIP lines are designed for voice, compressing the sounds as much as possible. When you compress modem tones or other tones, they often just don't make it to the other end so that equipment can understand them. Your alarm company may be able to hook up your alarm system so it transmits on the Internet instead of a phone line, but that doesn't make much sense since there's a good chance the Internet won't work when the alarm goes off (Murphy's Law). Keep a real phone line for your burglar or fire alarm!

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Ground Start Trunks Some PBXs are setup to use Ground Start Trunks. A Ground Start Trunk is dead for outgoing calls until the phone system puts ground on the phone line (the ring side) for maybe a quarter second. Ground Start trunks are thought to help reduce "glare," where someone is trying to make an outbound call and actually gets a new incoming call because the trunks are all pretty busy. Most VoIP boxes and cable company boxes only offer Loop Start Trunks, where all it takes to get dial tone is to go off-hook. Even if the VoIP box or cable box can be optioned to provide a Ground Start Trunk, the provider probably doesn't know what a Ground Start Trunk is. Some older phone system required a different trunk card for a Ground Start or Loop Start Trunk. Some have jumpers or programming options for Ground Start/Loop Start. In any case, if your system requires a Ground Start Trunk and you give it a Loop Start Trunk, you won't be able to call out, incoming calls may or may not ring, all the lines may be busied out so no lines work at all, and you may get phantom ringing (incoming calls with nobody there).

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... E911 If people are used to dialing 911 to get the police, and it doesn't work, it could be bad. Most VoIP providers give you stickers to put on the phone that say "911 might not work." Write the local non-emergency number on the sticker.

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Telephone Book Listings You may or may not be listed in the white or yellow pages, or 411.

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Caller ID Displayed The name and/or number that people see on their Caller ID box when you call them may not be yours, and it may even say Cellular Call, Out-of-Area or Unavailable when you call someone (depending on who the VoIP provider rents their numbers from).

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... VoIP Voice Mail Some VoIP providers force your calls to go to their Voice Mail if they aren't answered in X rings. Ifyou don't want to use their voice mail, that can be a problem.

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Network Down Option Most VoIP providers will automatically forward calls to the number of your choice if their main system can't communicate with your VoIP device. This is critical: Put your cell or some other number in that field! Read the SLA (Service Level Agreement) carefully for any service you decide to use for incoming calls. Keep in mind that 99% uptime means your phone number won't work for over 7 hours out of the month. A 99.99% uptime means that your phone number won't work for over 4 minutes a month. The uptime numbers probably won't include intended downtime for maintenance of the servers or routers at the VoIP provider's data center, normally done in the middle of the night. That could add an hour or more of downtime a month (which you essentially never see on a phone line / voice T1 from the real phone company). If you're just using VoIP for outbound, getting cut-off once in a while or not being able to make outbound calls once in a while isn't a big deal (especially when you consider the savings over real phone lines). Not being able to receive incoming calls could cost you a lot more than the savings.

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Network Down Option Here is an example SLA from a business VoIP provider: XXX will credit its customers with a half of the month's charges for down-time caused by failure of it's server/switch that exceeds three hours in any month. VoIP has some inherent risks with interruptions of bandwidth and Customer Premise Equipment (CPE), like routers and ATAs, so naturally this is not covered. You should have confidence in our server/switch, and we back it up.

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Fax Works OK with some VoIP providers (you may need a "special" line/device). The reason faxes won't work is that the fax is using tones to communicate, like a modem. VoIP lines are designed for voice, compressing the sounds as much as possible. When you compress fax tones, they often just don't make it to the other end so that equipment can understand them.

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Modems Might work at slower speeds? Probably not. The reason modems won't work is that the modem is using tones to communicate. VoIP lines are designed for voice, compressing the sounds as much as possible. When you compress modem tones, they often just don't make it to the other end so that equipment can understand them.

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Credit Card Machines They don't use fast modems, but they still may not work on VoIP lines.

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... TV Set-Top Boxes Some cable or satellite set-top boxes have an option in programming to make it work with VoIP. Probably won't work without your changing something.

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Water, Gas or Electric Meters Some utilities have spent big bucks to install modems on their meters so they can read them remotely. There's some chance that the modem won't work with a VoIP line. When your utilities are shut off, you'll know for sure.

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Echo Sometimes you just can't get rid of it. It depends what's causing it

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Incoming DTMF Digit Recognition Sometimes Automated Attendants or Voice Mail Systems don't recognize DTMF digits when people call in, usually intermittently.

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Automated Attendant or Voice Mail Disconnect Some VoIP devices don't send a disconnect signal (like the real Phone Company usually sends). That means that when the outside party hangs-up after leaving a message, there may be a lot of silence or busy signals at the end of the Voice Mail message. Likewise, if someone calls in and hangs-up before making a selection on the Automated Attendant, the now disconnected call will end up ringing the phone programmed to get calls if someone just "waits" and doesn't dial an extension number (doesn't make the real person doing this happy). Many companies solve that problem by disabling 0 (the operator) entirely. Screw the stinkin' customer.

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Ringing Some VoIP devices will only ring a single phone. The phone company provides 5 REN worth of ringing. Most VoIP devices provide less. Many provide under 75VAC, which is the minumum a phone company is supposed to supply (VoIP companies aren't really phone companies - even though they claim to be, so they don't have to adhere to any standards).

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Garbled Voice Test it before you commit. Test it at different times of the day, and with different loads on your own network. Even if it sounds good to you, call many people and ask them how you sound. The VoIP providers think if the other party sounds good to you, you'll think their service is great. In reality, you may sound garbled to the other party, and it may be at a low volume. Where you put the VoIP device on your network may make a difference. A phone that connects with a USB or sound card connection (screen phone) will be very dependent on what you're doing on that particular PC. It would be best to do nothing while you're on a call. When you test the VoIP quality, be sure to have someone call you from that line when you're on a regular phone line. Most VoIP service providers have learned that if they make the call sound OK to the person using the line locally, their service won't be cancelled for quality issues as quickly. In many cases, they tilt the bandwidth so that the call sounds fine to the local caller, while it's garbled or choppy to the person on the other end. Try it many times, at different times of the day, before deciding whether to keep the service (most offer a 30 day moneyback deal of one kind or another).

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Hiss There's a hiss, or background white noise on some VoIP lines. Sometimes it's there all the time, sometimes just on some calls. Listening to the background noise on these calls is very tiring if you have to be on the phone all day.

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Drop-outs / Cut-offs Test it before you commit. Test it at different times of the day. It's often worse at different times of the day, depending on your type of Internet connection (T1, DSL, cable, etc.) and the general traffic at your ISP / on the Internet. If there are a lot of people watching/downloading movies in your neighborhood at the same time, VoIP could become very garbled. If you're planning to use VoIP between two locations (like an office and branch office or home worker), consider using a VPN (Virtual Private Network). A VPN will encrypt the SIP (VoIP) packets that carry the conversation (and any other data you send like and spreadsheets, etc.). That encrypted connection is called a VPN tunnel. VPN routers are inexpensive and easy to setup these days. You'll need one for each end of the connection. The reason to encrypt your VoIP traffic is to prevent your ISP from blocking/degrading the quality of VoIP calls by messing with the SIP packets, which are easy to identify as they go through their routers. Why would they do that? Because they probably are or own a phone company in addition to offering broadband. If your VoIP sounds terrible, you're more likely to switch to their phone service (which is almost always a better quality than VoIP, even if they call it VoIP themselves).

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Delay After Dialing Some VoIP providers have a long delay after the last digit dialed before your call goes through. That can sometimes be fixed by adjusting the number of digits they're expecting. Sometimes their service is just screwed up at different times of the day (or during a full moon?). Sometimes a particular VoIP phone might require that you hit * or # after your number, to start dialing.

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... Support Before committing, call or VoIP customer service a few times to see if you can live with that level of support.

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... What happens if you don't like the VoIP service after a while? It's better to think about this now, rather than when it happens. Paying an extra fee to drop the service before the contract is up isn't that bad. Making sure now that you can get phone service from another vendor is important.

Cable & VoIP Telephone Service Checklist See if these things work before you drop the Phone Company... What happens if the VoIP company goes out of business? It's better to think about this now, rather than when it happens.

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