Meridian America 61 用户手册

2.01 The SL-1 and console line circuit packs each contain eight line

circuits (see Fig. 

 The SL-1 line pack can use all eight circuits,

each circuit interfacing to an SL-1 set. The console line pack uses pairs

of line circuits to interface to attendant consoles: one pair may be used
from the upper four circuits and one pair from the lower four to
interface to two consoles.

Line circuits on the SL-1 line pack are automatically

powered up during signaling and transmission. The connected
circuit pairs on the console line pack are continuously powered on.

2.02 For SL-1 set connections. one pair of wires is used 
transmission and a second pair for signaling (see Fig. 2-2). For
attendant console connections, two pairs of wires are used for
transmission connections and two pairs for signaling connections. These

 Lions:

(a) terminate the loop tip and ring conductors with a balanced

600-ohm termination:

 provide 

 V power, phantomed over the transmission and

signaling pairs, to the set or console terminals:

 provide a measure of isolation of foreign potentials on the loop

from portions of the transmission and signaling circuitry;

 convert from the 2-wire transmission path of the loop to a 4-wire

transmission path:

 provide analog-to-digital and digital-to-analog conversion 

transmission signals.

2.03 The circuit pack includes two common multiplexing circuits to:

(a) interface the individual line circuits with the peripheral bus

signaling channel:

 retime digital signals received from the peripheral bus;

 decode address information received from the peripheral bus and

enable individual line circuits during selected time slots.

2.04 The information and signaling relevant to the SL-1 set or console
passes through the line circuit pack and is multiplexed with information
from other circuit packs. A multiplex loop connects the input and
output of up to two Peripheral Equipment 

 shelves to the Common

Equipment 

 where switching takes place (see Fig. 2-2 and 2-3).

2.05 The line circuits and common circuitry of the pack are mounted

on a 12.5 in 

 by 10 in 

 printed circuit board. The

front of the pack is equipped with two pack extractors and a Light
Emitting Diode 

 The rear of the pack is equipped with a

connector capable of accepting 80 pins. Ten of these circuit packs may
be mounted in one PE shelf but not to exceed 50% of the packs in a
cabinet.

3