Nortel Networks 553-3001-211 manual Card interfaces, Line interface units

NT8D09 Analog Message Waiting Line card Page 541 of 894

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” on page 30.

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 (will 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.

Circuit Card Description and Installation