No ringback tone from 81c PABX from Incoming TELCO CO trunk

[cable_bunny]

Dear Gents
Our 81c Nortel has analogue CO trunks provided by the TELCO Company. There is an analogue COT pilot line configured for incoming calls to the MMail auto attendant. The auto attendant is working fine until today that I noticed whenever I call the pilot CO Trunk, and the auto attendant answers to please dial the extension, I dial the extension but I dont hear a ringback tone from the PABX extension line. The called party extension answers no issues. When I used and test an extension to extension calls, ringback tone is okay. Cannot hear a ringback tone only for Incoming calls using the CO trunk. Only happen today.
I used to hear the ringback from the extension whenever I used the incoming CO trunk before.
Any inputs and advise please.
thank you and regards

 

[Firebird Scrambler]

It's possible that the 2 wires on the analogue trunk have recently been swapped over. You could try to swap them over on the frame and see if the problem still persists?.

This used to be a problem if the analogue trunks were earth calling or ground start etc.

Firebird Scrambler

Nortel & Avaya Meridian 1 / Succession & BCM / Norstar Programmer

Website =

http://somertel.net

linkedin

 

[cable_bunny]

Thanks F.Srambler. I have checked our COT analogue trunks in the MDF but it's still the same wirings as before.
There were no changes on the COT. This issue had happen only when we experienced power fluctuation on Site a couple of days ago.
We have 5 COTs all configured as incoming calls going to the MMail auto attendant. All 5 COTs behave the same.
Any comments and thoughts please.
Thanks

 

[Firebird Scrambler]

Thanks for the reply. It wasn't quite what I had meant to say. It was common in the UK and I expect other countries for the 2 wires to get swapped over in the Network from the exchange "Telco" to the customer site. It usually happens when a jointer remakes a multi pair cable and forgets to check the polarity on the two wires.

What I used to do was to take along a test phone with polarity lights and check the status against working circuits etc. You can also use a voltmeter to text the lines. Also it's good to check the voltage at the same time.

Firebird Scrambler

Nortel & Avaya Meridian 1 / Succession & BCM / Norstar Programmer

Website =

http://somertel.net

linkedin

 

[cable_bunny]

Hi F.Scrambler. I'll check/test the COTs and reply soon.
Many thanks