Nortel Circuit Card, Installation Manual, Page: 551 / 908

NT8D09 Analog Message Waiting Line card Page 551 of 906
Circuit Card Description and Installation
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 110 on page 552 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.