Nortel Networks 1000 - Manual (Page 34)

34 Overview
of the ground connection to the tip lead for a specific length of time. The
length of time 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.
Nortel Communication Server 1000
Circuit Card Reference
NN43001-311 02.06 Standard
27 August 2008
Copyright © 2003-2008 Nortel Networks
.