Digital Signal Transmission 1.By varying an electrical signal when it passes over a wire that is typically made of copper. 2.By varying the power of light as sent over a glass optical fiber. 3.By varying the radio waves sent through space, which is commonly referred to as wireless communications.
Main Types of Electrical Materials MaterialDefinitionExamples InsulatorDifficult for electrical current to flow Plastic, paper, rubber, dry wood, air, pure water, glass Semi- conductor Electrical flow easily controlled Carbon, germanium, gallium arsenide, silicon ConductorEasy for electrical current to flow Metals such as Copper, gold, silver, solder, water with ions, human body
Popular Copper Media Standards TIA (Telecommunications Industry Association) and EIA (Electronic Industries Alliance) work together to publish commercial building telecommunications cabling standards TIA/EIA-568-B which defines how to use the pins on the connectors on the ends of the cables. IEEE (Institute of Electrical and Electronic Engineers) publishes LAN standards such as IEEE802.3 which will define cable requirement.
Coaxial cable Gradually outdated from LAN Can run for longer distances than either STP or UTP Less expensive than fiber-optic cable though it is expensive than STP or UTP Still popular for TV and home internet service
STP (Shielded Twisted Pair) cable Shielding provides better electrical signals by reducing noise and attenuation. Shielding makes the cable more expensive, heavier and hard to bend.
STP - 3 insulations Total 3 insulations: 1.Each thin wire is covered in color-coded plastic insulation 2.Each pair of wires is twisted with a insulator called a pair shield around them 3.All the wires in the cable (usually 4 pairs) are covered by a shield called the overall shield.
ScTP (Screened Twisted Pair) ScTP is also called FTP (Foil Twisted Pair) ScTP does not have pair shield. Thus, it has only two insulations: wire insulation and overall shield. Cheaper than STP
UTP (Unshielded Twisted Pair) Flexible and easy install Offer the same data speeds Inexpensive RJ45 connector (RJ11 is for phone cable).
UTP cable categories UTP cable category PurposeComments Category 1TelephoneNot suitable for data Category 2Token Ring4Mbps Token Ring Category 3Telephone and 10BASE-T 10Mbps Category 4Token Ring16Mbps Token Ring Category 5Ethernet10BASE-T and 100BASE- T Category 5eEthernetSame cable and connector. Support gigabit Category 6EthernetSupport 1Gbps. May support 10Gbps
TIA/EIA568-A and B pin outs Pin #Function568A wire color568 B wire color 1TD+White/GreenWhite/Orange 2TD-GreenOrange 3RD+White/OrangeWhite/Green 4UnusedBlue 5UnusedWhite/Blue 6RD-OrangeGreen 7UnusedWhite/Brown 8UnusedBrown
Straight through cable Can be used to connect PC and other network equipments to LAN hub/switch Wire 1 and 2 are used to transmit data Wire 3 and 6 are used to receive data
Cross-over cable It is used to connect two same equipments such as PC-to-PC. Both ends need to send data on pin 1 and 2; receive data on pin 3 and 6. In 568B, one end has white/orange and orange on pin 1 and 2; another has white/orange and orange on pin 3 and 6. In 568B, one end has white/green and green on pin 3 and 6; another end has them on pin 1 and 2.
Rollover cable Usually used as console cable. Change the sequence on another end. Most commonly used to connect a computer terminal to a router’s console port. This cable is typically flat to help distinguish it from other types of network cabling. It gets the name rollover because the point- outs on one end are reversed from the other end.
Connector and Adapter The 8 Position 8 Contact (8P8C) (often called RJ45) connector Cross over adapter
Optic media Fiber-optic cable has the strongest ability to resist EMI (electromagnetic interference), RFI (Radio Frequency Interference) Fiber’s bandwidth is much higher than any other media. Fiber is highly secure and it is easy to detect intrusion. Fiber uses light signal transmission and its attenuation is much less than electrical signals. Its length could be very long
Duplex A duplex communication system is a system composed of two connected parties or devices which can communicate with one another in both directions. (The term duplex is not used when describing communication between more than two parties or devices.) Half duplex cannot send/receive in same time.
Optical fiber cable components Core: usually made by silicon dioxide (from sand) Cladding: coated on the core to reflect light and seal it inside Buffer: physical protect cladding and core Jacket: prevent damage from abrasion, solvents and other contaminants
Multimode fiber Fiber with large (greater than 10 μm) core diameter may allow light coming in with different angles. (It must be in limit of acceptance cone)
Single mode fiber Fiber with a core diameter less than about ten times the wavelength of the propagating light and it can only allow light coming in from one direction.
Some thumbnail rules Inexpensive LED transmitter is usually used with inexpensive multimode cable Expensive laser transmitter is usually used with expensive single mode cable Single mode cable with laser transmitter can support longer cable distance than multimode cable with LED transmitter.
Optical Fiber Connector (Optional) LC/PC connector and SC/PC connectors have caps covering the ferrules Other connectors are ST, SC, MT, MT-RJ, MU, etc, etc
Wireless tech introduction Infrared Bluetooth Microwave Radio Wi-Fi In general, wireless network is secondary because of two concerns: speed and security. But, it does offer mobility and convenience.
Main wireless components Access point: linking wireless network to the wired world. Wireless NIC on each hosts in the network Wireless hub, switch and router: functioning as same as regular wire connected equipments
WLAN standards organizations IEEE published the WLAN standard. FCC (Federal Communication Commission) will specify restriction on power and radio frequencies in US. Industry Canada is taking care of radio frequency usage in Canada. Frequency use/approval may be different in various areas, regions and countries.
Question Any question? If you do not have question, please search internet and collect more information of those cables, connectors and standards. 1.Please be comfortable to draw the shape of popular connectors. 2.Please be familiar with those organizations’ full name and main responsibilities.