Nortel Networks Circuit Card User Manual

 NT8D15 E&M Trunk card

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. 

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)