AT&T StarLAN 10 Manual de Instruções descarregar pdf (Página 314)

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101

DID Trunk (TN753)

The DID Trunk Circuit Pack interfaces eight central office trunks arranged for Direct

Inwrd Dialing ((DID) and the TDM bus.

Figure 3-15 shows the following DID Trunk unique

circuitry:

● Port Input/output (1/0) circuit

● Eight port circuits.

Port I/O Circuit: This circuit consists of bus expanders for communication between the

on-board microprocessor and the port circuits.

It receives commands from the on-board

microprocessor and distributes them to the individual port circuits. It also accesses the port

circuit scan points and passes the information to the on-board microprocessor.

Port Circuits: The eight port circuits are identical.

Each port circuit consists of a codec,

balance network, trunk interface unit, and loop termination circuit.

The codec is a 4-wire circuit that converts the NPEs output to an analog signal. Likewise, it

converts the analog signal from the Central Office (CO) to a PCM signal to the NPE.

The trunk interface unit contains a hybrid, a 2-wire interface circuit, and control circuitry.

The hybrid circuit converts the 4-wire analog signal from the codec to a 2-wire analog signal

that is connected to the analog line by the 2-wire interface circuit. The control circuitry

controls loop current, internal signal gain, terminating resistance, battery feed shutdown,

and battery reversal. The circuit pack accepts both dial pulse and touch-tone signaling.

The loop termination circuit provides a fixed impedance to the DID trunk.

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AT&T StarLAN 10 Manual de Instruções Página 314

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