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Can anyone help me in solving Time Slipping on D500? The PBX is having an issue with clock slipping every 2-3 weeks. Lately, it seems be happening every week. 2 PBXs are linked in a master-slave setting. The master PBX is set for network clock. When the master sees the time slipping, it uses its own clock acting like a master clock. We cannot receive/send fax. Is this T1 issue? Or, PBX timing issue? I'm wondering whether we should change the T1 carrier.

Most likely a carrier issue.
Escalate and get supervisor at test center.
Was it working with same carrier and then problem started? Many times its hard to get carrier tech to admit it is them or even know what to do to correct.

Have you seen anything besides slips? Do you have a way to monitor the T-1 or can the LEC monitor it? If this is PBX to PBX there is no network clock in it so if you are purely having slips it can't be the LEC.

The only way the LEC would be giving you timing is if this were a very old circuit installed prior to CPE providing timing, which I highly doubt.

Then the main should not be set to network?
Is this a networked system or 2 cabinets at 1 site.?

Not if it's PBX to PBX. There is no line to sync off of.

This is a three year on-going issue. First 8 months, they came to our site and tested everything that they can think of from both T1 carrier and PBX vendor. T1 carrier installed Adtran to monitor the line remotely, as well. Without the network clock, these 2 PBX run wild, and FAX will not work. When the problem re-occur, I can reset the PBX side by disconnecting the link to the slave PBX. The Master PBX will try to sync with T1 clock. The slave PBX is located in the next building from us. We use this for intercom.

I hope I answered all the questions. Also, the time slipping is happening to other PBX in one of our building from the same T1 carrier. The PBX is manufactured by Toshiba. This PBX is not the one I mentioned about these 2 PBX (Master & Slave). It is completely a different PBX box. The same error happening on this PBX. Since the Toshiba PBX is not linked to T1-PRI, just a T1 analog, the problem is not recognized by users.

Guess we need more info. I thought he meant 2 cabinets with 1 t1, not a point to point;
After re-reading I think I am CORNFUUZZED!

I don't know Panasonic and they may have different terms, but you can't time off the network when there is no network there. A point to point T-1 has no network source. So the first thing that needs to be understood as brokeda says is this a point to point, or does it teminated in some phone company equipment?

In my office, I have a T1 circuit box.
The T1 is going into the master PBX (Panasonic D500), from the D500, there is a line coming out the D500 connected to another PBX (Slave, this is another panasonic, but I don't know the model #) in other building where terminated. The Slave PBX is there so that we can use extensions to call their phones.