Nortel Networks Circuit Card User Manual
Page 45
Overview
Page 45 of 906
Circuit Card
Description and Installation
Message waiting
Line cards that are equipped with the message waiting feature receive
notification that a message is waiting across the Card LAN link (IPE cards).
On cards that drive a message waiting light, the light is turned on by
connecting the ring side of the telephone line to the –150 V dc power supply.
When the line card senses that the telephone has gone off-hook, it removes
the –150 V dc voltage until the telephone goes back on-hook. Line cards that
use an interrupted dial tone to indicate message waiting do nothing until the
receiver is picked up. The line card then interrupts the dial tone at a regular
interval to indicate that a message is waiting.
In both cases, the message waiting indication will continue until the user
checks his or her messages. At that time, the system will cancel the message
waiting indication by sending another message across the Card LAN link or
network loop.
Analog line supervision
Analog line supervision features are used to extend the answer supervision
and disconnect supervision signals when the line card is connected to an
intelligent terminal device (Key system or intelligent pay phone). Two types
of analog line supervision are provided:
•
battery reversal answer and disconnect supervision
•
hook flash disconnect supervision
Battery reversal answer and disconnect supervision
Battery reversal answer and disconnect supervision is only used for calls that
originate from the terminal device. It provides both far-end answer
supervision and far-end disconnect supervision signals to the terminal device.
In an intelligent pay phone application, these signals provide the information
necessary to accurately compute toll charges.
In the idle state, and during dialing and ringing at the far end, the line card
provides a ground signal on the tip lead and battery on the ring lead. See
Figure 8 on
. When the far-end answers, these polarities are reversed.
The reversed battery connection is maintained as long as the call is
established. When the far-end disconnects, the system sends a message that