Nortel Networks Circuit Card 311 - Manual (Page 33)

Line cards 33
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 continues until the user
checks his or her messages. At that time, the system cancels 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 "Battery reversal answer and disconnect supervision sequence"
(page 35)
. 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 causes
the line card to revert the battery and ground signals to the normal state
to signal that the call is complete.
Hook Flash disconnect supervision Hook flash disconnect supervision
is only used for incoming calls that terminate at the terminal device (typically
a Key system). See
Figure 9 "Hook flash disconnect supervision sequence"
(page 36) . The disconnect signal is indicated by the removal of the ground
connection to the tip lead for a specific length of time. The length of time
Nortel Communication Server 1000
Circuit Card Reference
NN43001-311 01.04 Standard
Release 5.0 23 May 2008
Copyright © 2003-2008, Nortel Networks
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