Nortel Networks 1000 - Manual (Page 29)

Line cards 29
The digital line interface card contains one or more digital line interface
units. See
Figure 5 "Digital line interface unit block diagram" (page 29) .
Each 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.
Nortel Communication Server 1000
Circuit Card Reference
NN43001-311 02.06 Standard
27 August 2008
Copyright © 2003-2008 Nortel Networks
.