Nortel Networks 311

Operation 605

Trunksidentiﬁed as possibly reverse wired are switched by software to loop

start processing after the second ring. This switching takes place on a

call-by-call basis. So 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 reversewired." When identiﬁed as positively

reversewired, the call is presented continuously from the ﬁrst ring. When a

reverse-wiredtrunk becomes correctly wired, the ﬁrst subsequent call clears

the threshold counter and normal ground start processing is implemented.

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.

Since the software expects to see a ground on the tip lead, it interprets

the end of the ﬁrst ringing signal as a switchhook ﬂash. But since 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.

The reverse-wiring compensation feature operates as follows. If an

apparent disconnect takes place immediately after the ﬁrst ringing signal,

the software time stamps the eventand temporarily remove the call from the

console loop key. If another such ringing/disconnect event occurs during

the No Ringing Detector (NRD) time, the trunk is considered "possibly

reverse-wired" anda threshold counter starts. Calls on trunks identiﬁed as

possibly reverse-wiredare presented to the attendant during the initial ring,

removed, and then continuously presented after the second ring. If a call on

a possibly reverse-wiredtrunk is abandoned before the attendant answers,

it is disconnected after the NRD timer expires.

A trunk identiﬁed as possibly reverse-wired is switchedby the software

to loop start processing after the second ring. This switching takes place

on a call-by-call basis. So if a previously correctly wired trunk becomes

reverse-wired, the nextincoming call is marked as possibly reverse-wired

and the threshold count begins.

Nortel Communication Server 1000

Circuit Card Reference

NN43001-311 01.04 Standard

Release 5.0 23 May 2008