AT&T System 25 User Manual
Page 423
Loop-Start Trunk
Modem
Modem
Simplest type of central office (CO) trunk. Calls are originated by
providing a dc path between the tip and ring leads. The CO detects
the loop
current
thus drawn and returns dial tone. Incoming calls are
signaled by the CO placing an ac ringing voltage between the tip and
ring leads. (The port circuit pack detects this signal.)
A device that modulates and demodulates signals transmitted over a
communications path. Used to connect Data Terminal Equipment to
the system’s analog ports. The system (optionally) provides a 212A
compatible conversion resource.
Pooling
Provides shared-use conversion resources that eliminate the need
for dedicated modems.
Multiline Voice Terminal
A terminal equipped with several call appearance buttons for the
same extension number. Allows
call at the same time.
Multiplexed
The simultaneous transmission
common transmission medium.
N e t w o r k
the user to handle more than one
of two or more signals over a
An arrangement of inter- and/or intra-location circuits designed to
perform specific functions.
Network Interface
Provided by the telephone company in three forms:
(1) RJ21X for trunk facilities other than tie trunks.
(2) RJ2GX for tie trunk facilities.
(3) RJ48X or RJ48G for DS1 Tie Trunk facilities.
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