Partner 7.0 system that has been in service for a couple years with no problems.
The system has 25 extensions, 4 outside lines, and NO voicemail at all.
This weekend, Outside line 2 started ringing for no reason. When they pick it up, no one is there, just a dial tone. They can make calls out on line 2, but as soon as they hang up, it starts ringing again.
When they hang up, it immediately starts ringing again. Caller ID works when there is an incoming call, but there is no one calling, it just rings. It keeps on ringing until they answer it, and there is no one there.
They finally disconnected Line 2 from the system just to stop the annoying ringing.
I tested the outside line with a butt set and everything works normal. But as soon as I plug it back into the Line 2 port on the system, it starts ringing again. I have monitored the traffic on line 2 and there is not a call coming in to cause the ringing.
So my thinking is there is something wrong withe the outside line, or there is some signalling issue with the phone company on line 2.
Now here is the weird part...
When I swap line 1 with line 2 (Connect line 1 to line 2 port and connect line 2 to line 1 port) everything works as it should. Calls come and go normally.
I have swapped all 4 lines around and everything works normal, EXCEPT when the Line 2 cable is plugged into the LINE 2 port.
If I plug the LINE 2 cable into any other port or if I plug any other line into port 2, it works fine.
I have power cycled the system, but I have not done an initialize, reload and restart. I have also replaced the line 2 cable from port 2 to the outside line.

I saw a post from last year that was similar but not exactly the same and the concesus was the port on the ACS was bad. I would tend to agree in this case also, except the system works fine as long as any other line except CO line 2 is plugged into Line 2 Port.
For now I have lines 1 and 2 swapped and the system is working. I just don't want to leave it that way, because most calls come in on line 1.

I am scratching my head on this one, any suggestions???
Thanks!

Have you checked the loop current on the CO lines?
But any way in the short term, sounds like you may have a bad line port on the ACS.

You could leave the lines swapped and reassign them on the phones so that they are in order- 2,1,3,4. That will Band Aid the problem but I agree you have a bad line port.

-Hal

Are these standard Loop Start CO Trunks? Have you tried reversing polarity?

Sam

Sounds like a "HOT" co loop current to me. Also, are they Centrex lines?

Loop current wouldn't come into play until the phone or line were off hook. If it were the line it would happen when you frogged it. I'd sure check the line to see what's different about it from the other 3 but doesn't sound like a line problem.

Can they receive actual incoming calls on line 2? I've had a CO line do this (on a Mitel SX50) it turned out to be a short on the service providers end. That was one time in 18 years. I agree it is wierd that it stops when you swap ports but I would have to agree with Michael & Hal too and say its the port going out.

I've had this exact same situation on a few R6 CO line ports. The fix was to replace the module and send in for repair...