Nortel Circuit Card 311 Reference page 29

The digital line interface card contains one or more digital line interface units.
See
digital line interface unit contains a Digital Line Interface Circuit (DLIC). The
purpose of each DLIC is to demultiplex data from the DS-30X Tx channel
into integrated voice and data bitstreams and transmit those bitstreams
as Bi-Polar Return to Zero, Alternate Mark Inversion (BPRZ-AMI) data to
the TCM loop. It also does the opposite: receives BPRZ-AMI bitstreams
from the TCM loop and multiplexes the integrated voice and data bitstream
onto the DS-30X Rx channel.
The 4-wire to 2-wire conversion circuit converts the 2-wire tip and ring leads
into a 4-wire (Tx and ground and RX and ground) signal that is compatible
with the digital line interface circuit.
TCM loop interfaces
Each digital phone line terminates on the digital line card at a TCM loop
interface circuit. The circuit provides transformer coupling and foreign
voltage protection between the TCM loop and the digital line interface
circuit. It also provides power for the digital telephone.
Figure 5
Digital line interface unit block diagram
To prevent undesirable side effects from occurring when the TCM loop
interface cannot provide the proper signals on the digital phone line, the
system controller can remove the ±15 V dc power supply from the TCM loop
interface. This happens when either the card gets a command from the
NT8D01 Controller card to shut down the channel, or when the digital line
card detects a loss of the 1 KHz frame synchronization signal.
Copyright © 2003-2008, Nortel Networks
.
Figure 5 "Digital line interface unit block diagram" (page
Nortel Communication Server 1000
Circuit Card Reference
NN43001-311 01.04 Standard
Release 5.0 23 May 2008
Line cards 29
29). Each