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

Page 574 of 894 NT8D14 Universal Trunk card

Figure 121

DID trunk, loop DR call connection sequence – incoming call from CO

A			Near end				Far end			B
			System					CO
		State			Signal/direction					Remarks
				Ground
				on tip/		High-
				battery		resistance
		Idle		on ring			loop
						Low-resistance loop			CO places a low resistance between tip and
Trunk seizure
									ring.
									Near end detects increase in loop current
						Address signaling			and makes trunk busy to all outgoing calls.
Outpulsing									CO applies addressing to the trunk in the
									form of battery-ground or loop pulses or
				Ringback					DTMF tones.
	A rings								Near end detects addressing, alerts terminal
				Battery on tip/					A, and provides ringback tone to CO.
2-way voice				ground on ring					When terminal A goes off hook, near end
connection
									trips ringback tone and provides answer
									super-vision by reversing battery and ground
									on tip and ring.
B goes on hook						High-resistance loop			If far end disconnects first, CO opens the
				Ground on tip/					loop.
		Idle		battery on ring					Near end detects drop in loop current and
									reverses battery and ground on tip and ring.
				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							CO detects battery/ground reversal and
									opens loop.
										553-AAA1138

553-3001-211 Standard 2.00 September 2004