DPC3941T gateway reboots after receiving a phone call

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@CCAndrew wrote:
Is your phone plugged in directly to the modem or going through your home wiring?

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My phone service goes through my home wiring and my home wiring includes an alarm system.  The rebooting does not seem to happen if I disconnect the home wiring and plug in a single phone into the modem.  Until I switched from Verizon to Xfinity in August, I did not have any phone problems.  The Xfinity installer disconnected my house phone wiring from Verizon and reconnected to the Xfinity modem.  Sorry I posted in the wrong community -- I am a new user.

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@CCAndrew wrote:
No worries, house phone wiring is hard to track down the cause. It takes time to eliminate the cause. Maybe check that your alarm is compatible and not causing issues. You could disconnect the alarm, hook the phone line back up going through the house wiring and see if the issue replicates

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Thanks!  My alarm system uses an RJ-31X connector to "sieze" the phone line ahead of all phones in the house.  I can try to disconnect at the RJ-31X.  Is there any way to find out what the modem doesn't like about my home wiring?  The modem log files are of no help and neither is the modem documentation.  If there is a house wiring problem, it doesn't stop the phone from working other than the reboots.  All phones have good dial tone, calls are loud and clear, and the modem can power all the ringers on my phones.  It would seem that the easiest solution would be to upgrade the modem firmware so that the modem doesn't reboot or to provide a way to control the conditions under which a reboot occurs.  It is unclear what useful purpose the rebooting servies and why Cisco programmed that behaviour into the modem.

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@CCAndrew wrote:
Usually if it’s rebooting, it’s acting like there’s a short somewhere. That’s the fun of troubleshooting phone wiring is eliminating everything one by one

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Is there some kind of line tester that can be used to test for a short or other line fault?  That would seem to be more efficient than trial & error guessing.  Obviously, my wiring can't have much of a short, since the ringers ring and there is good call volume.  Also, the modem doesn't reboot on outgoing calls.  That might indicate the short is not continuous but time dependent or that there is a bug in the modem software.  Even if my house phone wiring isn't perfect, having a modem that reacts by rebooting doesn't seem to be a useful feature/behavior.

None of the above answers resolved my problem.  I have a Panasonic KX-TG885 cordless phone/answering machine.  After it answers a call where the caller hangs up during the outgoing message, the DPC3941T gateway restarts, and phone and internet connectivity is lost for about 5 min while the reboot is in progress.  The gateway will also reboot if I use a cordless handset to answer a short call that lasts about a minute or so.  The rebooting does not occur with phone calls lasting longer than 5 minutes or so --- no matter if the answering maching initially answers or if the call is manually answered with a cordless handset.  I have had this problem since I started Comcast service on 20 Aug.  It does not matter if the KX-TG885 is connected to my house wiring or directly connected to the RJ-11 port on the back of the DPC3941T.  I have been able to replicated this identical behavior using a different cordless phone system (Panasonic KX-TG6445).  I have had Xfinity technicians come to my house twice and they were unable to solve the problem.  Neither of these cordless phone systems is listed as being incompatible on the "Equipment Incompatible with Xfinity Voice" web page (https://www.xfinity.com/support/articles/incompatible-equipment-phone).  Prior to having Xfinity service, I have used both of these cordless phone systems without issue on FIOS voice phone service.  Based on this experience, I would conclude that the Xfinity DPC3941T has a flaw that makes it incompatible with some Panasonic coredless phone systems.