Nortel Networks 553-3001-211 manual NT8D09 Analog Message Waiting Line card Page 539

NT8D09 Analog Message Waiting Line card Page 539 of 894

The NT8D09 Analog Message Waiting Line card also provides:

•600 ohms balanced terminating impedance

•analog-to-digital and digital-to-analog conversion of transmission and reception signals for 16 audio phone lines

•transmission and reception of Scan and Signaling Device (SSD) signaling messages over a DS-30X signaling channel in A10 format

•on-hook/off-hook status and switchhook flash detection

•20 Hz ringing signal connection and automatic disconnection when the station goes off-hook

•synchronization for connecting and disconnecting the ringing signal to zero crossing of ringing voltage

•loopback of SSD messages and Pulse Code Modulation (PCM) signals for diagnostic purposes

•correct initialization of all features at power-up

•direct reporting of digit dialed (500-type telephones) by collecting dial pulses

•connection of –150 V dc at 1 Hz to activate message waiting lamps

•lamp status detection

•disabling and enabling of selected units for maintenance

Figure 107 on page 540 shows a block diagram of the major functions contained on the analog message waiting line card. Each of these functions are described in the following sections.

Circuit Card Description and Installation