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COMSPHERE 392xPlus Modems
Glossary-2 November 1996 3920-A2-GN31-30
automatic dial standby When operating in Dial Backup mode, this function forces the modem to periodically
check the quality of the leased line. If the leased line is found to be at normal operating
condition, the modem disconnects from the dial network and continues normal operation
over the leased-line network.
automatic rate control
Modems adjust their signaling rate based on current line conditions.
backbone network The primary route from a control modem to its first tributary when the communications
network contains extended control modems.
backplane A common bus at the rear of the COMSPHERE 3000 Series Carrier connecting each
circuit card slot to the SDCP and/or SDU. It also distributes low-voltage ac power to
each slot.
baud
A unit of signaling speed that is equal to the number of symbols per second. This is not
necessarily the same as bits per second, although the terms are frequently interchanged.
Bisync
Binary Synchronous Communications. An IBM
r
communications protocol that has
become an industry standard. It uses a defined set of control characters and
control-character sequences for synchronized transmission of binary-coded data between
stations in a data communications system.
bit A contraction of binary digit. A bit, which is the smallest unit of information, represents
the choice between a one or a zero (sometimes called mark or space).
bps
Bits per second. Indicates the speed at which bits are transmitted across a data
connection.
broadcast A method of transmission. The simultaneous transmission to two or more
communicating devices.
buffer A storage device used to compensate for differences in the data flow rate when
transmitting data from one device to another.
byte
A sequence of successive bits (usually eight) handled as a unit in data transmission.
carrier The rack mounting that contains 17 slots: 1 control slot for an SDU and 16 modem slots.
See data carrier.
carrier-mount A modem that is designed for installation in a COMSPHERE 3000 Series Carrier and
used at central-site operations.
CCITT An advisory committee (Consultative Committee on International T
elephone and
T
elegraph) established by the United Nations to recommend communications standards
and policies.
channel A path for electrical transmission between two or more points. Also called a circuit, line,
link, path, or facility.
character A letter, figure, number, punctuation, or other symbol.
character echo A way to check the accuracy of data transmission by sending to the monitor (displaying)
all the characters being transmitted.