1. The Eyes & Ears of the system
Chapter 8
Alarms: The First Line of Defense
Sensors
The Eyes & Ears of the system
© 2001 National Burglar & Fire Alarm Association 8-1

2. Perimeter Sensor Objective
To Detect an Event.
An Open Door.
A Broken Window.
Entry Thru Wall, Roof or Floor.
Entry Thru Outer Perimeter.
© 2001 National Burglar & Fire Alarm Association 8-2 6 6

3. Perimeter The perimeter is the outer reaches of a system.
For a building system it is the walls, floor and ceiling.
For an outdoor system it is a fence or perhaps the outer edge of the sensors pattern.
© 2001 National Burglar & Fire Alarm Association 8-3

4. Magnetic Reed Switch Switch changes with magnet away from switch.
Magnetic reed switches seal the working parts of the switch in a glass tube to protect the contacts from corrosion.
This enables the switch to last longer and operate more consistently.
Contacts are enclosed In hermetically sealed tube.
© 2001 National Burglar & Fire Alarm Association 8-4 19 19

5. Mechanical Switches Simple & inexpensive. Easily defeated.
Subject to corrosion.
Plunger switches are primarily used in door or window frames or as tamper switches on splice boxes or panel cabinets.
Most types of these switches are not sealed from the environment and are subject to corrosion.
One problem unique to these switches is that the plunger itself can get stuck in the pushed down position preventing the switch from sensing that a door or window has opened.
© 2001 National Burglar & Fire Alarm Association 8-5 27 27

6. Door & Window Switch False Alarms
Doors & windows must be tight fitting & locked.
Door & window contacts must be free of paint & varnish.
Make sure there is no door or window warping.
Any broken contacts should be replaced immediately.
Perimeter Protection: window and door contacts. Window and door contacts may be inlayed in door, need to be installed close to hinge, caution on dual doors and doors sheathed in metal need larger magnet (3/4”). Window contacts may be used on window frames and sliding doors and are usually glued with clear silicone. Steel commercial doors need larger contacts, which will allow for a 2” gap.
© 2001 National Burglar & Fire Alarm Association 8-6

7. Re-inforced or Sun Film Coated
Foil Patterns
18 ”
Plate Glass
Tempered Safety
Conductive foil is attached to the glass with its own self adhesive back or a varnish is applied to the glass first and the foil is applied to the varnish.
In either case a protective coating of varnish is applied over the foil to reduce the possibility of damage.
When the foil is applied it is stretched to enhance the possibility that is will break in all cases when the glass is broken.
If solar film is applied over top of the foil or applied to the other side of the glass it will tend to hold the glass together when it breaks and reduce the effectiveness of the foil.
So a window with solar film will require a foil pattern that covers more of the window.
Re-inforced or Sun Film Coated
Multi-pane
© 2001 National Burglar & Fire Alarm Association 8-7 21 21

8. Foil False Alarms
Foil contains lead & needs to be replaced every 3-5 years due to extreme summer weather.
It can be easily scratched or damaged.
Scratched or damaged foil can cause false alarms.
© 2001 National Burglar & Fire Alarm Association 8-8

9. Shock or Vibration Detectors
Vibration causes contacts to open.
Tension on contacts is adjustable.
Contact opening may be too fast.
Inexpensive device detects attack before entry.
Setting of sensitivity is difficult and can result in false alarms.
Short fast opening of contacts may be too fast for some controls or some zone settings.
© 2001 National Burglar & Fire Alarm Association 8-9 22 22

10. Mercury Devices Vibration of mercury sealed in tube causes an alarm.
Closed
Open
Vibration of mercury sealed in tube causes an alarm.
Sensitivity adjusted by varying tube angle.
Inexpensive devices detect attack at glass break. Peel and stick self adhesive pads provide easy installation.
Short fast event is too quick for some controls or some zones.
Adhesive can wear out and sensor may fall off the window , particularly if window is not cleaned correctly before installation.
Cord can harden in sunlight over time an cause sensor to remain in place and fail to detect a break-in.
Sensitivity can be reduced in cold weather.
© 2001 National Burglar & Fire Alarm Association 8-10 23 23

11. Piezo Electric Devices
Small crystal vibrates to produce electricity when glass is broken
Can be self contained or be wired to a processor.
Device responds to the frequency of glass breaking.
Device must be mounted to the glass with an adhesive that will not dampen or buffer the transmission of vibrations of the glass.
Solar film will reduce the effectiveness of these devices.
Segments of cracked glass will rub together and cause false alarms.
Sensors can operate without power because the piezo crystal vibrates when the glass breaks and generates electricity.
© 2001 National Burglar & Fire Alarm Association 8-11 25 25

12. Shock Sensors
Impact
At Rest
Sensor consist of disks or metal balls which rest on a rail or set of contacts until disturbed. When at rest the disks or balls completed the circuit between the rails or contacts.
Vibrations cause the disks or balls to move which opens the circuit.
Processors count the number of times the circuit is opened and how long it remains open and react.
Sensitivity settings at the processors allow the installer to calibrate or adjust the system to react to the environment being monitored.
Specific processors or processor settings may be required for different types of materials. Settings will be different for example for glass than for solid walls.
Shock sensors are used to monitor automatic teller machines, fences, coin boxes, and conduits. They can also be used on solid walls or for glass break detection.
All sensors on a particular loop should monitor the same type of construction.
Use simple sensors connected to processors that decide when to initiate an alarm.
© 2001 National Burglar & Fire Alarm Association 8-12 24 24

13. Screens Screen is laced with thin wire.
Alarm circuit is run through the wiring.
Screens provide an effective way to sense an entry through an open window. This allows the alarm user to open the window for ventilation while the system is active.
© 2001 National Burglar & Fire Alarm Association 8-13 26 26

14. Interior Sensors Combination Motion Sensors Ultrasonic Detectors
Microwave Detectors
Passive Infrared Detectors
Photoelectric Detectors
Audio Processors
© 2001 National Burglar & Fire Alarm Association 8-14

15. Motion or Space Detection
When people move it changes the environment.
Detectors are designed to react to these changes while ignoring changes
that normally happen in the environment.
What changes occur when people move?
The detector must respond!
© 2001 National Burglar & Fire Alarm Association 8-15 7 7

16. Avoid False Alarms!!
What changes occur when there are no people present or moving?
Detector must NOT respond!
© 2001 National Burglar & Fire Alarm Association 8-16 8 8

17. Disguised Sensors Various types of sensors can be
concealed or disguised as:
1. Duplex Electrical Outlets.
2. Thermostats.
3. Speaker Grills.
4. Smoke Detectors.
5. Light Fixtures.
© 2001 National Burglar & Fire Alarm Association 8-17 9 9

18. Motion Sensor Uses Trap Channel Spot Volumetric
Trap Detection
Broad or wide detection in high traffic areas or expected travel paths of an intruder .
Spot Detection
Detection on a particular object or high value areas such as safes, vaults, storage areas, money rooms.
Channel Detection
Narrow detection in an area where an intruder is expected to cross.
Volumetric Detection
Wide or broad detection in a defined area. Sensors are located and adjusted so that a human is detected moving at a rate of one step per second, taking four steps (#3 or #2 extent of UL protection).
© 2001 National Burglar & Fire Alarm Association 8-18 15 15

19. Older Motion Sensors Ultrasonic Microwave Photoelectric
Listens to reflected sound, & responds to a change from movement.
Microwave
Monitors for a reduction in level of transmitted energy which may be caused by motion.
Photoelectric
Responds to an interruption the light beam sent between a transmitter & receiver.
The term ultrasonic refers to sound above the range of human hearing. The ultrasound leaves the detector and is carried by the air in the room until it bounces off any hard surface and is returned to the receiving transducer. If nothing has changed the original transducer frequency will be received with its strength somewhat diminished, since each time it hits an object and bounces off it some of the energy is absorbed. The sound energy entering the detector is converted by the receiving transducer into electrical energy.
Microwave sensors use radio waves for detecting a moving target. The returned energy, or lack of returned energy, is analyzed to determine if there is an intruder in the room. Some transmitted energy is reflected off the floor, ceiling and walls. Because the floor, ceiling and wall are stationary they reflect a consistent amount of energy. When an object moves in the room it reflects at a slightly different frequency. This change in the returned frequency is known as the Doppler shift.
The space the beam covers, an invisible cylinder of light between the transmitter and receiver, is small but it can be used to cover a wide area. Modern photoelectrics are designed to detect an interruption of a beam of pulsed infrared light which is being projected from a light source and received by a photocell. Pulsing the light at varying frequencies means that the intruder who have to duplicate the exact pulse rate to defeat the system.
© 2001 National Burglar & Fire Alarm Association 8-19

20. infrared energy levels
Passive Infrared
Responds to
changes of
infrared energy levels
within specific
fields of view.
A passive sensor designed to respond to changes of infrared energy levels within specific fields of view.
Passive Infrareds (PIR’s) use pie shaped span of view, should not be installed for an area longer then 100’ (usually 35’ to 40’), are tripped by walking across the span of view. Infrareds will not read through glass or walls, and looks for ambient temperature change.
© 2001 National Burglar & Fire Alarm Association 8-20 33 33

21. Poor or No Catch Motion Gradual Change +
Gradual
Change
If there is a gradual change, such as a target moving toward the
sensor, the signal level will rise at a very slow rate.
This can result in a poor or no catch.
In fact, the moving target could get averaged in with the background.
© 2001 National Burglar & Fire Alarm Association 8-21 35 35

22. Good Catch Motion Rapid Change +
Rapid Change
When that same target moves across the field of view, it results in a fast unbalanced change, which causes the signal level to reach the alarm threshold.
This can be either a negative or positive threshold voltage.
© 2001 National Burglar & Fire Alarm Association 8-22 36 36

23. PIR Patterns Pet Alley
Think! Pets climb, jump, & go places they shouldn’t. If a pet can cause a false alarm assume it will.
© 2001 National Burglar & Fire Alarm Association 8-23

24. Dual Technology Sensors
Microwave
PIR
Overlapping patterns of the two technologies provide stability preventing false alarms
in harsh environments.
Dual detectors rely on overlapping patterns of two technologies to provide stability in harsh environments that would cause false alarms if only one of the technologies were used.
© 2001 National Burglar & Fire Alarm Association 8-24 45 45

25. What Can Cause Motion Detector False Alarms?
helium balloons (especially mylar)
pets
bugs on the lens
curtains
All interior equipment should be dusted, vacuumed around, etc for bugs & spiders.
Should be installed 3’ to 4’ away from vents.
PIR’s are a common cause of false alarms due to ceiling fans, balloons, pets, decorations, vertical blinds, etc
© 2001 National Burglar & Fire Alarm Association 8-25

26. Audio discriminators listen for the sounds of forced entry;
Glassbreak Sensors
Audio discriminators listen for the sounds of forced entry;
Glass Breakage
Splintering Wood
Etc.
A sound discriminator is a device capable of continuously monitoring the audio environment and listening for selected frequencies generated by forced entry.
Even though some advertise detection of all forced entry, most sound discriminators are used to detect glass breakage.
When glass breaks it generates frequencies much higher than normal background noises. When these higher frequencies occur they are detected and the alarm is activated.
UL testing verifies that detectors listed for primary detection will detect breaking of:
1/8” and 1/4” thick plate glass.
1/4” thick tempered glass.
1/4” thick laminated glass.
1/4” thick wired glass.
Most sound discriminators can detect these various types of glass breaking up to 50 feet away if aimed directly at the glass, and up to 35 feet away when installed a right angles (90o) to the windows.
Glass Break Detectors – are usually installed on ceiling or wall, 6’ to 25’ form large fixed glass area. They are trip at the sound or frequency of breaking glass. Dual tech glass breaks use frequency of breaking glass and percussion to trip system
© 2001 National Burglar & Fire Alarm Association 8-26 40 40

27. Glass Break Sensor False Alarm Sources
Single technology glass break sensors can mistake the following for glass breaking:
Clinking glasses
Strong or heavy vibrations
Pots & pans hitting each other
Other sounds similar to the sound of glass breaking
USE DUAL TECHNOLOGY SENSORS!
© 2001 National Burglar & Fire Alarm Association 8-27

28. shorts the metal strips
Pressure Mats
Pressure on the mat
shorts the metal strips
together.
Pressure mats can be concealed under carpets or rugs.
Installation may require pulling up carpet and re-stretching and re-securing it after laying down the mat.
Must be left out of the system when people are home.
Can be tripped by large pets.
Can be tripped or damaged by heavy objects including planters and furniture.
Mounted under carpet in area likely to be walked upon.
© 2001 National Burglar & Fire Alarm Association 8-28 42 42

29. Stress Sensors Mount under joists in area to be covered.
Stress sensors react to the flexing of the material that they are mounted to.
Units are attached to the joists with epoxy.
Sensors are usually connected into a processor which enables the sensitivity of the sensors response to be adjusted.
Stress sensors are used on stairs, joists, etc.
© 2001 National Burglar & Fire Alarm Association 8-29 43 43

30. Mats & Stress Sensor False Alarm Sources
Both are stable until furniture is rearranged around or on top of them
© 2001 National Burglar & Fire Alarm Association 8-30

31. Manual Devices Foot rail. Holdup button. Money clip.
Portable duress sensor.
Touchpad Activated
Manual alarms use manually-operated switches that a person can activate without risking detection. Several types of switches are commonly used.
Foot rail- A duress alarm, often used at cashiers windows, in which a foot is placed under the rail, lifting it, to initiate an alarm signal.
Holdup button- A mechanical switch used to initiate a holdup alarm signal: usually constructed to minimize accidental activation.
Money clip- A sensor device which activates a signaling device when money is removed from between the contacts.
Portable duress sensor- A device which can be carried on a key chain or clipped on a belt which indicates an alarm when pressed.
Touchpad Activated- A silent or audible alarm can be manually activated by entering a code different from the normal code or pressing a single or combination of buttons.
© 2001 National Burglar & Fire Alarm Association 8-31 3

32. Manual Devices False Alarm Sources
Improper user training
”Single action" buttons
“Single action” money clips
Batteries in wireless buttons that are not replaced when the manufacturer recommends.
© 2001 National Burglar & Fire Alarm Association 8-32

33. Fire Alarm Sensors Heat Detectors. Flame Detectors.
Smoke Detectors.
Heat Detectors.
Flame Detectors.
Manual Pull Stations.
© 2001 National Burglar & Fire Alarm Association 8-33

34. Condition Monitoring Alarms Can Be Used to Monitor:
Medical Emergencies.
Low or High Temperature.
Failure of Equipment.
Operation of Equipment.
(Generators, Sump Pumps , Etc..)
Water or Moisture
Power Failure
© 2001 National Burglar & Fire Alarm Association 8-34

35. Carbon Monoxide Gas Alarms
Indicates an unacceptable level of carbon monoxide gas is present in a room.
May indicate a failure in a furnace or improper ventilation in a room with a fireplace or wood stove.
Even limited exposure to high levels of carbon monoxide can be lethal to humans and animals.
© 2001 National Burglar & Fire Alarm Association 8-35

36. Alarms: The First Line of Defense
1- Introduction
2- What is an Alarm System
3- What is A False Dispatch
4- Impact of False Dispatches
5- Causes of False Dispatches
6- Preventing False Dispatches
7- User Controls
8- Sensors
9- The Control
10- The Central Station
11- How Authorities Respond
12- What to expect for Alarm Co.s
13- The Alarm Ordinance
14- Sources of Information
15- Site Survey
Next
Chapter
5 Minute
Break
10 Minute
Break
30 Minute
Lunch
60 Minute
Lunch
© 2001 National Burglar & Fire Alarm Association 8-36