Avaya 1000 Series, Reference

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Digital line interfaces
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 Server and return incoming call status information to the Call
Server 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.
Card control functions
Control functions are provided by a microcontroller and a Card LAN link on the digital line card.
A sanity timer is provided to automatically reset the card if the microcontroller stops functioning
for any reason.
Functional description
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