AT&T StarLAN 10 Manual de Instruções descarregar pdf (Página 426)

100

101

FUNCTIONAL DESCRIPTION

operates the appropriate relay.

The relays control circuitry provides the proper

signaling for loop start trunks. The trunks support touch-tone dialing and dial pulse

signaling.

The surge protection circuit provides overvoltage lightning surge

protection for the circuit pack.

MET Line (TN735)

The MET Line Circuit Pack interfaces four Multibutton Electronic Telephone (MET) lines and

the TDM bus. The MET Line unique circuitry consists of four port circuits as shown in Figure

3-14.

NPE

ON-BOARD

MICRO-

PROCESSOR

TO MET

TERMINALS

MET Line (TN735) Unique Circuitry

Figure 3-14.

Circuits

● Port

The

four port circuits are identical. Each port circuit consists of an analog port, a

digital port, and an electronic power feed device.

The analog port circuit consists of

a codec, a hybrid circuit, an electronic battery feed, and a power filter. The codec,

hybrid circuit, and power filter perform the same function as in the Analog Line

Circuit Pack (TN742). The electronic battery feed provides talking battery to the MET

set, produces a controlled dc battery feed current for short and long loops, and

detects when a MET set user lifts a receiver. The digital port circuit provides a full

duplex channel over two 2-wire pairs. All outgoing lamp

button depression (BT, BR) information is carried on these

(LT, LR) and incoming

channels. Ringing and

3-25

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