Nortel Networks 553-3001-211 manual State

Page 42 of 894 Overview

Figure 7

Call connection sequence – near-end originating call

Far-end

station

through

PSTN

Near-end

station

System

State

Line card unit idle

Call request

Outpulsing

(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

Low-resistance loop

Dial tone

Addressing signals

Dial tone

Ringback (or busy)

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.

Near-end station goes off hook. Battery current is drawn causing detection of off-hook state. CPU determines unit terminal number (TN) and assigns message timeslots.

Dial tone is applied to the near-end station from the system.

Near-end station dials number (loop pulsing or DTMF tones).

The system detects start of dialing and removes dial tone.

The system decodes addressing, routes call, and supplies ringback tone to near-end station if far- end station is on hook. (Busy tone supplied if far-end station is busy.)

When call is answered, ringback tone is removed , and call is cut through to far-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-AAA1114

553-3001-211 Standard 2.00 September 2004