Nortel Circuit Card 311 Reference page 546

546 NT8D09 Analog Message Waiting Line card
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Card interfaces
The analog message waiting line card passes voice and signaling data
over DS-30X loops and maintenance data over the card LAN link. These
interfaces are discussed in
Line interface units
The analog message waiting line card contains 16 identical and
independently configurable line interface units (also referred to as circuits).
Each unit provides 600-ohm impedance matching and a balance network in
a signal transformer/analog hybrid circuit. Circuits are also provided in each
unit to apply the ringing voltage onto the line synchronized to the ringing
current zero crossing. Signal detection circuits monitor on-hook/off-hook
status and switchhook flash detection. Four CODECs are provided to
perform A/D and D/A conversion of line analog voiceband signals to digital
PCM signals. Each CODEC supports four line interface units. The following
features are common to all units on the card:
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Card control functions
Control functions are provided by the following:
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Copyright © 2003-2008, Nortel Networks
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connection of –150 V dc at 1 Hz to activate message waiting lamps
lamp status detection
disabling and enabling of selected units for maintenance
Transmission and reception of Scan and Signaling Device (SSD)
signaling messages over a DS30X signaling channel in A10 format.
Loopback of SSD messages and pulse code modulation (PCM) signals
for diagnostic purposes.
Correct initialization of all features, as configured in software, at
power-up.
Direct reporting of digits dialed (500 telephones) by collecting dial
pulses.
Connection of –150 V dc at 1 Hz to activate message waiting lamps in
two telephones in parallel. The two telephones must be the same type or
the neon series resistor in each telephone must be 54 K ohms or greater.
Lamp status detection (does not detect a failure of either lamp when
operating in parallel).
Disabling and enabling of selected units for maintenance.
40 mA to telephones with short circuit protection.
a microcontroller
a card LAN interface
Nortel Communication Server 1000
Circuit Card Reference
NN43001-311 01.04 Standard
Release 5.0 23 May 2008
"Intelligent Peripheral Equipment" (page 21).