Nortel Networks 553-3001-211 manual State

Overview Page 41 of 894

Figure 6

Call connection sequence – near-end station receiving call

Far-end

station

through

PSTN

Near-end

station

System

State

Line card unit idle

Alert

Near-end station

off hook

(2-way voice connection)

Near-end station

on hook

Line card unit idle

Far-end station

on hook

Line card unit idle

Signal/direction

	High-
Ground on tip/	resistance
battery on ring	loop

Ringing

Low-resistance loop

High-resistance loop

	High-
Ground on tip/	resistance
battery on ring	loop
High-resistance loop
Ground on tip/	High-
	resistance
battery on ring	loop

Remarks

No battery current drawn.

Far-end station goes off hook and addresses (dials up) near-end station. The system receives the incoming call on a trunk and determines that the call is for a specific unit terminal number (TN) and assigns message timeslots.

The system applies 20 Hz ringing to ring lead.

Near-end station goes off hook.

The system detects increase in loop current, trips ringing, and cuts call through to near-end station.

If near-end station hangs up first, the following occurs: Line card detects drop in loop current. CPU removes timeslot assignments.

Line card unit is ready for the next call.

If far-end station hangs up first, the following occurs: The system detects disconnect signaling from trunk. CPU removes timeslot assignments. Person at near-end station recognizes end of call and hangs up.

Line card unit is ready for the next call.

553-AAA1113

Circuit Card Description and Installation