HT813 doesn't always answer answer FXO


Hi Guys

Hoping for some help here.

I have 3 HT813 with the FXO ports connected to analogue lines on an old PABX.

All three intermittently don’t answer incoming calls even though they ring for 40 seconds plus, one only answers 50% of the time.

Problem seems worse under heavy load.

Any ideas.

Thanks in advance


it depends on the network infrastructure
it depends on the NAT mode
it depends on how you figured out HT813
lower keep alive to 15 seconds.

As you can see there are many variables to go on a sure answer.


Thanks for your reply damiano70

Does the HT813 not answer the analogue FXO line before it does anything else so these settings would only effect routing and onward calls via SIP or have I got it wrong.


Is the HT813 receiving ring from the old pbx and sending the call to a sip client? or is it providing sip via the fxs to the pbx?


Hi scottsip

Yes it receives ring from PABX and sends to SIP client


eliminate internet and run the sip client on the nic that the ht813 is on and see if is doing the same, if not then id be looking at routers…


no internet or routers.

Config is

PABX analogue line into FXO N/W connection out of HT813 into a switch and the SIP to ESPA convertor (destination of call) is in same switch


what is doing the dhcp… what sort of switches… managed/smart managed or dumb?


no dhcp fixed ip for destination


Am I to understand that the analog lines are coming into the HT from the PBX and then to some other IP device at the other end?


Yes that’s exactly correct.


Play with the loop current disconnect settings. Try 400, 600 &, 750ms.


The problem isn’t that it doesn’t disconnect and we don’t get a busy signal. We use tone disconnect and this works fine. The problem is that it sometimes the HT813 just sits there with the incoming analogue line (FXO) ringing in and its as if it can’t hear it so doesn’t answer.


Did you normalize this extension in PBX?
Usually internal and external call use different settings, and your description match this. One work, second not.


All extensions on this PBX are internal.

We thought we did have the HT813 set as an internal line.

But i am asking the question on here as we don’t have any settings from PABX guys they just say its BS6305 which I don’t have a full copy of and is what we thought we had set to.


I’m not familiar with that one, you can try contact GS directly.