Phone Line Failover for PBX


Have PBX running with several phone sets on a bridge network. My internet connection occasionally goes down so want to have a phone line (POTS line) back up that will switch over automatically when the PBX loses connection with the remote SIP server. Need calls in and out.

Thinking about using the HT-813 to connect the phone line to the PBX but need some help with the 813 configuration. Not sure what is needed - Please help. Thanks


What PBX do you have


And please describe what you mean by a bridge network. If you mean that the PBX and phones are remote from one another, where does the HT need to reside…where the phones are or where the PBX is?


Free PBX


The PBX, phones and HT all on same IP sub net on the LAN side of a router, router WAN connected to the Internet. PBX and HT set with static IP


The FXO port needs to be set up as a trunk on the PBX. The PBX needs to have outbound rules established that encompass how you envision seeing it being used - (which extensions, as a failover, dial rules, etc.). You will then need to tell the HT how to route an incoming call.

The issue will be the calls in as you have been using SIP, any POTS line number will be unknown to external callers unless you tell them in advance. I assume that you will have the SIP provider route to the POTS as a disaster recovery scenario so that the number need not be made known.

As you are aware, the HT is only able to handle one POTS line call at a time, be it in or out calling. This may present a limitation and you may want to consider a gxw410X gateway to increase the call capacity.


Okay, so how do I tell the HT to route the incoming call? I think that’s my biggest problem. I’ve tried to direct it to the PBX “Unconditional Call Forward to VOIP: 100@”
(ip not my real ip address) and get dead air.


And I assume you have an extension 100?

is the FXO port registered on the PBX? Have you done a wireshark of the call to see the messaging?


No, the FXO port is not registered on the PBX. So I need to setup a trunk up on the PBX specifically to handle the FXO coming into the PBX aside from my normal trunks?


Yes you should register the HT.


Thanks for info! Will see what I can do.