Instruction manual

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