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The signaling and control operation of the card performs many functions
which are handled by different functional units. Some of the functions of the
signaling and control portion of the E & M card are:
•
Communications between the card and the CPU
•
Monitor signals from the trunk interface and generate a message when
required for each state change
•
Decode received messages and activate/deactivate configuration and
interface relays PCM loopback for diagnostic purposes
•
Disable and enable units for maintenance
•
Drive Light Emitting Diode (LED) on faceplate
•
Decode outpulsing messages (one per digit) from the CPU to drive
outpulsing relays
— Make break ratios (20pps, 10pp1, 10pps2) are downloaded by
software.
•
Control of A/mu-law operation
Microprocessor
The E & M trunk has a microprocessor which performs a number of
operations. On power up a self test of the circuitry on the card is performed.
The self-test can also be requested by a command entered in maintenance
programs. The card faceplate Light-Emitting Diode (LED) is lit while the self
test is performed. If the self test passes, the faceplate LED flashes three times
and stays lit until the card is enabled in software. If the test fails, the LED
stays lit (does not flash).
Signaling interface
All signaling messages for the trunk are three bytes long. The messages are
transmitted in channel zero of the DS30X in A10 format.
Configuration information for the E & M trunk is downloaded from the CPU
at power up and by command from maintenance programs. Seven
configuration messages are sent. One message is sent to each unit (4) to
configure trunk type, signaling type, balance impedance etc. Three messages
are sent per card to configure the make/break ratio, A/mu-Law operation.
NT8D15 E&M Trunk Card
Option 11C and 11C Mini
Page 393 of 544
Technical Reference Guide
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