Nortel Networks 553-3001-211 manual NT8D14 Universal Trunk card Page 567

NT8D14 Universal Trunk card Page 567 of 894

Figure 116

Ground start call states – incoming call from CO/FX/WATS

System (near) end

CO / FX / WATS (far) end

Tip open,	battery on ring
Ground on tip,	battery on ring

High-resistance loop		Low-resistance loop
	Near end
Idle	disconnects
		far end
	Far end	disconnects
	disconnects	first
	Near end
	disconnects
	first (Note 2)
		Near end
	Ringing	answers,
		ringing is
Far end	Assignment	removed
originates	to loop key	(Note 1)

Note 1: The far end may reverse battery and ground upon receipt of attendant answer.

Note 2: The near end provides a high-impedance (>150k ohms) disconnect signal of at least 50 ms before reconnecting the ground detector.

553-AAA1133

A trunk identified as possibly reverse-wired is switched by the software to loop start processing after the second ring. This switching takes place on a call-by-call basis. Thus, if a previously correctly wired trunk becomes reverse-wired, the next incoming call is marked as possibly reverse-wired and the threshold count begins.

If the threshold count exceeds its limit, an error message is printed and the trunk is registered as “positively reverse wired.” Once identified as positively reverse wired, the call is presented continuously from the first ring. When a

Circuit Card Description and Installation