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

Page 588 of 894 NT8D14 Universal Trunk card

Figure 132

Two-way, loop OAID, TIE trunk call connection sequence – incoming call from far-end PBX

A			Near end				Far end			B
			System					PBX
		State			Signal/direction					Remarks
				Ground
				on tip/		High-
				battery		resistance
		Idle		on ring			loop
						Low-resistance loop			Far end PBX seizes trunk by placing a low
Trunk seizure
									resistance between tip and ring.
									Near end detects increase in loop current
						Address signaling			and makes trunk busy to all outgoing calls.
Outpulsing									Far end sends battery-ground or loop
									pulses, or DTMF tones.
	A rings			Battery on tip/					Near end detects addressing and alerts
									terminal A.
2-way voice				ground on ring					Terminal A goes off hook. If answer
connection
									supervision is required by far end, reverse
									battery and ground are applied to tip and ring.
									Far end monitors loop current during 2-way
									voice connection.
B goes on hook						High-resistance loop			If far end disconnects first, it opens the loop.
				Ground on tip/
		Idle		battery on ring					Near end detects drop in loop current and
									restores normal battery and ground.
				Ground on tip/
A goes on hook				battery on ring					If near end disconnects first, it reverses
						High-resistance loop			battery and ground on tip and ring.
		Idle							Far end detects battery/ground reversal and
									opens loop.
										553-AAA1146

553-3001-211 Standard 2.00 September 2004