Avaya Nortel Communication Server 1000 Reference page 42

Overview
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.
Each TCM loop interface circuit can service loops up to 3500 ft. in length when using 24 gauge
wire. The circuit allows for a maximum ac signal loss of 15.5 dB at 256 KHz and a maximum
DC loop resistance of 210 ohms.
Signaling
The digital line interface units also contain signaling and control circuits that establish, monitor,
and take down call connections. These circuits work with the system controller to operate the
digital line interface circuits during calls. The circuits receive outgoing call signaling messages
42 Circuit Card Reference
Comments? infodev@avaya.com
July 2011