Nortel Networks 1000 - Manual (Page 429)

Functional description 429
The digital line interface circuits also contain signaling and control circuits
that establish, supervise, and take down call connections. These circuits
work with the on-card microcontroller to operate the digital line interface
circuits during calls. The circuits receive outgoing call signaling messages
from the CP and return incoming call status information to the CP over the
DS-30X network loop.
The digital line interface contains two Digital Line Interface Circuits (DLIC).
Each digital line interface circuit provides eight identical, individually
configurable voice and data interfaces to eight digital telephone lines.
These lines carry multiplexed PCM voice, data, and signaling information
as TCM loops.
The purpose of each digital line interface circuit is to de-multiplex
data from the DS-30X Tx channel into eight integrated voice and data
bitstreams. The circuits then transmit those bitstreams as Bi-Polar Return
to Zero, Alternate Mark Inversion (BPRZ-AMI) data to the eight TCM loops.
They also perform the opposite action: they receive eight BPRZ-AMI
bitstreams from the TCM loops and multiplex them onto the DS-30X Rx
channel. The two digital line interface circuits perform the multiplexing and
de-multiplexing functions for the 16 digital telephone lines.
The digital line interface circuits also contain signaling and control circuits
that establish, supervise, and take down call connections. These circuits
work with the on-card microcontroller to operate the digital line interface
circuits during calls. The circuits receive outgoing call signaling messages
from the Call Processor and return incoming call status information to the
Call Processor over the DS-30X network loop.
TCM loop interface circuit
Each digital telephone line terminates on the NT8D02 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 battery voltage for the digital telephone.
To prevent undesirable side effects from occurring when the TCM loop
interface cannot provide the proper signals on the digital phone line, the
card microcontroller can remove the ±15 V dc power supply from the
TCM loop interfaces. This happens when either the microcontroller gets
a command from the NT8D01 controller card to shut down the channel,
or the digital line card detects a loss of the 1 KHz frame synchronization
signal. The ±15 V dc power supply signal is removed from all 16 TCM loop
interface units at the same time.
Each TCM loop interface circuit can service loops up to 3500 ft. in length
when using 24-gauge wire. They support a maximum ac signal loss of
15.5 dB at 256 KHz and a maximum dc loop resistance of 210 ohms.
Nortel Communication Server 1000
Circuit Card Reference
NN43001-311 02.06 Standard
27 August 2008
Copyright © 2003-2008 Nortel Networks
.