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 (BTU).

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 (Private Branch Exchange) 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 ◆ Techniqueinwhichphysicalcircuits(asopposed to virtual circuits) are transferred to complete connections. Contrast with packet-switched networks.

Clock ◆ Timing signal used in synchronous transmission.

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