Data Communications Definitions

Attenuation

Attenuation is a reduction in strength or deterioration of an electrical signal as it passes through a transmission medium. Attenuation generally increases with frequency, cable length, and the number of connections in a circuit. Attenuation is measured in decibels (dB). In optical fiber cable, attenuation (loss of light) is caused by Rayleigh scattering, absorption, reflection, diffraction, and transmission losses. Attenuation limits the length of data communication cables.

Backbone

Generally, a backbone is the more permanent part of a communications network that carries the heaviest traffic. Usually, a vertical arrangement connects floors in a multi-story building. However, the same function may be served by a lateral backbone for horizontal distribution in a low, wide building.

Bend Radius

Bend Radius is the radius a cable can bend before the risk of breakage or increase in attenuation occurs.

Bus

1. A bus is a data path shared by many devices.
2. A bus is a linear network topology in which all workstations are connected to a single cable. On a bus network, such as Ethernet, all workstations receive all transmissions; only the workstation that the information is addressed to will use the information. Contrast with ring and star.

Crossover

A crossover is a conductor that connects to a different pin number at each end.

Crosstalk

Crosstalk is the phenomenon in which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel, generally related to wire placement, shielding, and transmission techniques.

Ethernet

Ethernet is a baseband LAN that connects routers, modems and network switches to computers, terminals, phones and printers within the same building.

Home Runs

Home runs are a pathway or cable between two locations without a point of access in between.

Impedance

A unit of measure, expressed in Ohms, of the total opposition (resistance, capacitance, and inductance) offered to the flow of an alternating current.

Jumper

A jumper is an assembly of twisted pairs without connectors used to join telecommunications circuits/links at the cross-connect.

Local Area Network (LAN)

A local area network, also known as LAN, is a non-public data communications network confined to a limited geographic area (usually within a few miles) that provides communication between computers and peripherals. The area served may consist of a single building, a cluster of buildings, or a campus-type arrangement. Owned by its user, LAN includes some type of switching technology and does not use common carrier circuits. Although, it may have gateways or bridges to other public or private networks.

Patch Panel

A patch panel is a cross-connect system of mateable connectors that facilitates administration.

Token

A token is a unique combination of bits used in LANs to grant permission to a station to transmit. In a ring network, the token circulates continuously; in a bus, it must be addressed.

Twisted Pair Cable

Twisted pair cable is a type of communications transmission cable in which two individually insulated wires are twisted around each other to reduce induction (thus interference) from one wire to the other. The pair may be surrounded by a shield, insulating, jacket, or additional pairs of wires.