Nortel Networks 553-3001-211 manual Signal/direction Remarks

Circuit Card Description and Installation

553-AAA1115

Overview Page 45 of 894

Figure 8

Battery reversal answer and disconnect supervision sequence

Far-end

station

System

Line card

Near-end

station

State

Line card unit idle

Call request

Outpulsing

(2-way voice connection)

Signal/direction		Remarks
	High-
Ground on tip/	resistance
battery on ring	loop	No battery current drawn.
Low-resistance loop		Near-end station goes off hook. Battery current is drawn
		causing detection of off-hook state. The system
		determines unit terminal number (TN) and assigns
Dial tone		message timeslots.
		Dial tone is applied to the near-end station from the
Addressing signals		system.
		Near-end station dials number (loop pulsing or DTMF
Dial tone removed		tones).
		The system detects start of dialing and removes dial tone.
Ringback (or busy)
		The system decodes addressing, routes call, and supplies
	Low-
		ringback tone to near-end station if far-end station is on
Battery on tip/	resistance	hook. (Busy tone supplied if far-end station is busy.)
ground on ring	loop	When call is answered (either absolute or assumed
		answer, as programmed), ringback tone is removed, call
		is cut through to far-end station, and battery is reversed
		to near-end station for duration of call.

Near-end station

on hook

Line card unit idle

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

If near-end station hangs up first, a high-resistance loop is presented to the system.

The system detects drop in loop current, removes timeslot assignments, sends disconnect signal to far-end station, and restores normal ground/battery polarity to the near- end station. Line card unit is then ready for the next call.

Far-end station

on hook

Line card unit idle

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

If far-end station hangs up first, the system detects disconnect signalling from the far end, removes timeslot assignments, and restores normal ground/battery polarity to the near-end station.

Near-end station detects battery reversal and goes on hook. Line card unit is then ready for the next call.

Note 1: Battery reversal signalling is a supervisory feature that is only used when the near-end station originates the call.