Nortel Circuit Card 311 Reference page 34

34 Overview
is programmed in LD10, and ranges from a minimum of 10 milliseconds to
a maximum of 2.55 seconds. See Software Input/Output Reference —
Administration (NN43001-611) for more information.
Digital line call operation
Digital line call operation is controlled entirely by use of messages between
the digital telephone and the system. These messages are carried across
the TCM loop interface. There is no call connection sequence similar to the
one used for analog telephone line operation.
Lineside T1 and E1 call operation
The lineside T1/E1 card's call operation is performed differently depending
on whether the T1/E1 link is configured to process calls in loop start mode or
ground start mode. Configuration is performed through dip switch settings
on the lineside T1/E1 card.
The lineside T1/E1 card performs calls processing separately on each of its
24 channels. Signaling is performed using the "A/B robbed bit" signaling
standard for T1/E1 communication.
A/B robbed bit signaling simulates standard analog signaling by sending a
meaningful combination of ones and zeros across the line that correlates to
the electrical impulses that standard analog signaling sends. For example,
to represent that an analog line interface unit is idle, the analog line card
provides a ground on the tip lead and –48Vdc on the ring lead. The
lineside T1/E1 card accomplishes the same result by sending its A bit as 0
(translated as ground on the tip lead) and its B bit as 1 (translated as –48V
dc on the ring lead). However, measuring the voltage of the ring lead on the
T1/E1 line would not return –48V dc, since actual electrical impulses are
not being sent.
Copyright © 2003-2008, Nortel Networks
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Nortel Communication Server 1000
Circuit Card Reference
NN43001-311 01.04 Standard
Release 5.0 23 May 2008