Nortel Circuit Card Installation Manual page 579

Figure 119
Ground start call states – incoming call from CO/FX/WATS
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.
High-resistance loop
Near end
disconnects
Idle
Far end
disconnects
Ringing
Far end
originates
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
NT8D14 Universal Trunk card
System (near) end
Near end
disconnects
first (Note 2)
Assignment
to loop key
Circuit Card
Page 579 of 906
Low-resistance loop
far end
disconnects
Near end
answers,
ringing is
removed
(Note 1)
553-AAA1133
Description and Installation
first