Glossary

BRI (Basic Rate Interface) ‹ A defined ISDN interface that includes two B channels and one D channel. Also known as 2B+D. B channels are used for voice and data while the D channel is generally used only for signalling within the telephone network.

Broadcast ‹ LAN transmission method used in bus topology networks that sends messages to all stations even though the messages are addressed to specific stations.

BTU ‹ See basic transmission unit.

CALC (Customer Access Line Charge) ‹ A Federal tariff charge, also referred to as an End User Common Line Charge (EUCL), or Subscriber Line Charge (SLC). Every ISDN line is charged one CALC or EUCL.

Call bumping ‹ The ability to receive an incoming call during a bonded outbound call.

CCITT (International Telephone and Telegraph Consultative

Committee) ‹ See ITU (International Telecommunication Union).

CD (Carrier Detect) ‹ RS-232 (V.24) control signal (on pin 8) that indicates that the local data communications equipment is receiving a signal from the remote DCE. (See RS-232.) Also called Received Line Signal Detector (RLSD) and Data Carrier Detect (DCD).

Centrex ‹ Local Public Exchange incorporating PBX facilities.

Channel ‹ 1) A path along which signals can be sent, for example data channel, output channel. 2) In data communication, a means of one-way transmission. 3) A function unit, controlled by the processor, that handles the transfer of data between processor storage and local peripheral equipment.

Channel aggregation ‹ Channel aggregation combines multiple physical channels into one logical channel of greater bandwidth. With BRI ISDN connections, channel aggregation would combine the two 64 Kbps B channels into a single, logical 128 Kbps channel.

Circuit-switching‹ Technique in which physical circuits (as opposed to virtual circuits) are transferred to complete connections. Contrast with packet-switched networks.

Clock ‹ Timing signal used in synchronous transmission.

CO (Central Office) ‹ The site where the local Telco switches reside for the telephone system's call routing and all other functions. This is the Telco side of the local loop. If the distance between your location and the central office switch exceeds 18,000 feet and/or the signal loss exceeds 35.0 dB, a repeater must be installed to allow ISDN service.

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