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NT8D09 Analog Message Waiting Line card
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
contained on the analog message waiting line card. Each of these functions
are described in the following sections.
shows a block diagram of the major functions
Circuit Card
Page 551 of 906
Description and Installation
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