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Page 628 of 894 NT8D15 E&M Trunk card
553-3001-211 Standard 2.00 September 2004
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/µ-Law operation.
Signaling and control
The signaling and control portion of the E&M trunk card works with the
system CPU to operate the card hardware. The card receives messages from
the CPU over a signaling channel in the DS-30X loop and returns status
information to the CPU over the same channel. The signaling and control
portion of the card provides analog loop terminations that establish,
supervise, and take down call connections.
Configuration information for the E&M trunk card is downloaded from the
CPU at power-up and by command from maintenance programs.
Configuration messages are sent. One message is sent to configure trunk and
signaling type. The other messages are sent to each card to select the make/
break ratio and the A-Law and µ-Law modes.
The signaling and control circuits on the card perform the following
functions:
• provide an interface between the card and the system CPU
— transmit PCM signals from each of the four units to one DS-30X
timeslot in A10 format (ready to send/clear to send—flow control,
handshake format)
— transmit and receive signaling messages over a DS-30X signaling
channel in A10 format
• decode received messages to set configuration and activate/deactivate
interface relays for PCM loopback diagnostic purposes
• decode outpulsing messages (one per digit) from the CPU to drive
outpulsing relays at 20 pps, 10 pps1 (primary), or 10 pps2 (secondary)