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Class

attenuation

reduction in signal amplitude or power as the signal travels through a transmission medium

backbone cabling

Network cabling that interconnects TCs and equipment rooms. This cabling runs between floors or wings of a building and between buildings to carry network traffic destined for devices outside the work area. It's frequently fiber-optic cable but can also be UTP. Also called vertical cabling.

cable plant

The collection of all the cables and connectors that tie a network together.

cable segment

A length of cable between two network devices, such as a NIC and a switch. Any intermediate passive (unpowered) devices, such as wall jacks, are considered part of the total segment length.

crossover cable

A type of patch cable that uses the 586B standard on one end and the 586A standard on the other end. This arrangement crosses the transmit and receive wires so that transmit on one end connects to receive on the other end. Often used to connect two devices of the same type to one another—for example, connecting a hub to a hub or a switch to a switch.

crosstalk

Interference one wire generates on another wire when both wires are in a bundle.

datagrade

A grade of cable that is suitable for data networking.

differential signal

A method for transmitting data in which two wires of opposite polarity are used. One wire transmits using positive voltage and the other uses negative voltage. Differential signals enhance signal reliability by providing a canceling effect on EMI and crosstalk.

electromagnetic interference (EMI)

A disturbance to the operation of an electronic circuit or its data caused by devices that emit an electromagnetic field.

encoding

The method used to represent bits on the medium.

entrance facility

The location of the cabling and equipment that connects a corporate network to a third-party telecommunications provider. It can also serve as an equipment room and the main cross-connect for all backbone cabling.

equipment room

A room that houses servers, routers, switches, and other major network equipment and serves as a connection point for backbone cabling running between TCs.

extended LANs

A LAN that is expanded beyond its normal distance limitations by using wireless communication.

fiber-optic cable

A cable type that carries data over thin strands of glass using optical (light) pulses to represent bits.

hertz (Hz)

A unit that expresses how many times per second a signal or electromagnetic wave occurs.

horizontal wiring

The network cabling that runs from the work area's wall jack to the telecommunications closet and is usually terminated at a patch panel. The total maximum
distance for horizontal wiring is up to 100 meters.

infrared (IR)

A very long wavelength light source that is in the invisible spectrum and can be used to transmit data wirelessly.

IrDA devices

Devices that use infrared signals to communicate. IrDA stands for Infrared
Device Association.

MDI crossed (MDI-X) devices

Network devices that connect by using RJ-45 plugs over
twisted-pair cabling. MDI-X devices transmit over pins 3 and 6 and receive over pins 1
and 2 of the RJ-45 connector.

medium dependent interface (MDI) devices

Network devices that connect by using RJ-
45 plugs over twisted-pair cabling. MDI devices transmit on pins 1 and 2 and receive on
pins 3 and 6 of the RJ-45 connector.

narrowband radio

Low-powered, two-way radio communication systems, such as those used in taxis, police radios, and other private radio systems. Also called single-frequency radio.

patch cable

A short cable for connecting a computer to an RJ-45 jack or connecting a patch-panel port to a switch or hub. Also see straight-through cable.

radio frequency interference (RFI)

Similar to EMI, except that RFI is usually
interference caused by strong broadcast sources. See also EMI.

RJ-45 jack

Used in the work area in wall plates and surface-mount boxes to plug a patch cable that connects a computer to the horizontal cable.

RJ-45 plug

The connector used to terminate twisted-pair cable for making patch cables. It has eight wire traces to accommodate a standard twisted-pair cable with four wire pairs.

satellite microwave

Microwave communication systems that send and receive data from satellites that maintain fixed positions in the sky.

spread-spectrum radio

Uses multiple frequencies simultaneously, thereby improving reliability and reducing susceptibility to interference over narrowband radio.

straight-through cable

A standard patch cable that uses the same wiring standards on both ends of the cable so that each wire is in the same corresponding location on both ends of the cable (pin 1 goes to pin 1, pin 2 to pin 2, and so forth). Also see patch cable.

structured cabling

A specification of how cabling should be organized in data and voice networks, regardless of the media type or network architecture.

telecommunications closet (TC)

Usually an enclosed space or room that provides
connectivity to computer equipment in the nearby work area. In small installations, it can also serve as the entrance facility. Typical equipment includes patch panels to terminate horizontal wiring runs, hubs, and switches.

termination

The attachment of RJ-45 plugs on a cable to make a patch cable or punching down the cable wires into terminal blocks on a jack or patch panel.

terrestrial microwave

Line-of-sight transmissions between microwave towers or between transmitters and receivers mounted on tall buildings, mountaintops, or other
locations with long, clear lines of sight.

transceiver

A device that transmits and receives. In wireless networking, an access point is a transceiver.

twisted-pair (TP) cable

One or more pairs of insulated strands of copper wire twisted around one another and housed in an outer jacket or sheath.

voicegrade

A grade of cable that is not suitable for data networking, but is suitable for voice communication.

wireless bridge

A wireless network arrangement that connects networks up to three miles (4.4 km) apart, permitting locations to be linked by using line-of-sight or broadcast transmissions.

work area

The location of workstations and other user device—in short, the place where people work with computers and other network devices.

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