Nortel Networks Circuit Card 311 - Manual (Page 546)

546 NT8D09 Analog Message Waiting Line card
• connection of –150 V dc at 1 Hz to activate message waiting lamps
• lamp status detection
• disabling and enabling of selected units for maintenance
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
"Intelligent Peripheral Equipment" (page 21) .
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:
• 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.
Card control functions
Control functions are provided by the following:
• a microcontroller
• a card LAN interface
Nortel Communication Server 1000
Circuit Card Reference
NN43001-311 01.04 Standard
Release 5.0 23 May 2008
Copyright © 2003-2008, Nortel Networks
.