I have a handful of sites doing this. All with the same carrier, same brand of PBX.
24 channels of PLAR. E&M
All PLARS will break out to different locations on the far end via the carrier and connect via T1 to multiple different types of PBXs.
All signaling bits are normally all ones on idle.
Clocking source doesn't seem to make any difference, line build out, DB, etc.
I never see reports of frame loss or slips. Neither does the carrier.
If I move the T1 to a different port on the PBX the problem follows the T1.
The carrier delivers circ to prem via IP and hands off via a router.
Ok here's the problem:
Someone will make an outbound call and on one channel and this causes all channels to seize outbound from the PBX.
Doesn't happen every time/call. Doesn't happen with every channel and isn't always consistent with any single channel.
Doesn't happen with all T1s connected to the same PBX or line card.
The PBX never reports an outbound call. It will show an incoming call if the far end picks up the handset because their end rang and this causes my end to ring.
I put a piece of equipment between the carrier and my PBX that would generate syslogs to show the origination of the calls and it always shows my PBX as the originator.
I'm trying to figure out what may be causing this. The carrier has convinced me that our protocols are matching.
The only thing I can think of is that perhaps we are getting a "false frame" for the 193 frame but I have no way to prove it.
Does anyone have any ideas at all?