Avaya Nortel Communication Server 1000 Reference page 391

Operation
Figure 110: Ground start call connection sequence - incoming call from CO/FX/WATS
Reverse-wiring compensation
The CS 1000 software includes a feature for detecting reverse wiring (connection of the near-
end tip and ring leads to the far-end ring and tip leads) on ground start trunks with far-end
answer supervision.
Ordinarily, an incoming call on a reverse-wired trunk without reverse-wiring compensation
presents ringing on the tip lead rather than on the ring lead. Because of the software expects
to see a ground on the tip lead, it interprets the end of the first ringing signal as a switchhook
flash. As the interval between ringing signals exceeds the switchhook flash time of 512
milliseconds, the software assumes a far-end disconnect. This causes the call to be presented
to a console loop key and then immediately removed.
Circuit Card Reference July 2011 391