I have a customer with a DXP Plus. every once in a while a call will ring in and the phones will ring, the customer will try to answer and they will only get dialtone. The person calling in hears a couple of rings, and then silence. I have replicated this one time. The provider has the hunt group set correctly, they do not have call waiting, or telco provided voicemail turned on. When I replicated the problem I was connected to the system and could see the realtime smdr records. there was no indication that the call that I placed that failed was ever seen by the smdr recorder.

Is it possible the caller hung up or was disconnected?

No. I experienced this as a caller into the system.

Is it PRI or Pots. Who is the carrier?

Have you followed: "Troubleshooting The DXPT1 Digital Carrier Transmission Option On The DXP Plus Digital Communications System"?

I will send you a PM with a link to view the document. The file also contains other pertinent information on the DXP Plus for you viewing pleasure

Sorry I should have mentioned sooner that these are POTS lines.

And the Carrier is Charter Spectrum (local cable company)

Without seeing a Black Box capture it would be hard to diagnose. Could be a fluke programming corruption of one phone in the hunt group or a hardware issue with the SRV-PLS or CPU board.

After playing musical lines. I believe that it may be isolated to an individual line card. possibly a single port on that card, but as they have more line cards than they are currently using I am going to fully take that one out of service.

Line cards cost almost nothing. They usually dont fail this way but worth a shot