If it does the basics, ie you can pick up, seize the line, dial out, hang up, get the phone to ring and answer, then effectively the SIP/VoIP side of things is sorted. Your remaining problem relates to how well the ATA emulates the interface at a BT Master Socket

If you can dial out, then DTMF is good enough. If you can hear a reasonable quality and similarly be heard, the the codecs [vocoders] are fine. I have a shed load available and have never had to fiddle with this. As for caller id, the range of choices is constrained enough that you can just try until you find one that works. This is purely local between the ATA and the phone, so if it works once, it should always work.

Like you, I am normally inclined to want to fix down every last setting. I would even want the ATA to have a simple menu where you just select the country and all the settings are done for you, But there are so many different standards - even within the UK - that I can see why ATA vendors don't do this. So I have accepted that I set what I know and I do the best I can with the rest. And that works for me.

It does work generally speaking. I can dial out and receive calls and the BT call guardian thing answers and asks my name, but weird things happen when the call is hung up with numerous beeps and sounds being heard for a few seconds after the caller has hung up, but before the line actually disconnects at the Grandstream/DECT phone end. This doesn't happen on the SPA112 which disconnects cleanly. I would like to be able to nail that down if possible. I am guessing that its related to signalling between the Grandstream and the BT 8500.

Like I said, change batteries on the BT8500, before trying to find a setting. It is probably cheaper than your time trying to find a fix. This cured my BT8600 of its random behaviour.

Try looking for "Loop Current Disconnect" in the Grandstream FXS Port page.

If disabled, enable, apply and update.

Changing this setting stopped the answerphone running for 30 secs or so after an incoming call is terminated using an HT801 V1 and BT Decor 2600 (corded handset with Trucall + answerphone).

I'd second this. All my original 6 Gigaset phones were used, from eBay. They all worked fine until 2 of them started being inconsistent. Batteries apparently fully charge OK, but we kept getting disconnections and a blank screen in the middle of a call. I replaced the 2 AAA batteries in each phone (highpowertech.com from China) with new Energizer rechargeables, and all is now fine.

In reply to a post by DFScale:

Like I said, change batteries on the BT8500, before trying to find a setting. It is probably cheaper than your time trying to find a fix. This cured my BT8600 of its random behaviour.

Noted. Will try that.

In reply to a post by cjn:

I'd second this. All my original 6 Gigaset phones were used, from eBay. They all worked fine until 2 of them started being inconsistent. Batteries apparently fully charge OK, but we kept getting disconnections and a blank screen in the middle of a call. I replaced the 2 AAA batteries in each phone (highpowertech.com from China) with new Energizer rechargeables, and all is now fine.

Thank you. I have also just received the N300A plus the Gigaset handsets today. Everything looks in a good clean condition. The handsets all powered up when dropped into their charger cradles which is a good start and are all charging as I type. I will hopefully get some time to set up the N300A tomorrow and we will see how it goes. This is worth knowing should any of the handsets play up.

In reply to a post by BarkingMad:

Try looking for "Loop Current Disconnect" in the Grandstream FXS Port page.

If disabled, enable, apply and update.

Changing this setting stopped the answerphone running for 30 secs or so after an incoming call is terminated using an HT801 V1 and BT Decor 2600 (corded handset with Trucall + answerphone).

Thank you. Due to the recent family emergency I haven't had much time to experiment for the last couple of days, but hopefully will be able to give this a try tomorrow.

Edited by TruthDigital (Wed 01-Oct-25 20:52:40)

I set up the N300A and C530 handsets yesterday and have to say it and they work very well. The batteries in the other two handsets either didn't hold power or just barely. I put two sets of fresh batteries into handsets 1 and 2, and the "good" sets into the other two. I ordered and have some more on the way to replace the latter. I have to say I am very pleased with it. Dialling out seems faster and the audio quality is very clear. I can also receive calls from both VOIP numbers assigned to my account.

In reply to a post by BarkingMad:

Try looking for "Loop Current Disconnect" in the Grandstream FXS Port page.

If disabled, enable, apply and update.

Changing this setting stopped the answerphone running for 30 secs or so after an incoming call is terminated using an HT801 V1 and BT Decor 2600 (corded handset with Trucall + answerphone).

This morning, I found and configured this setting on the Grandstream and it does indeed solve the problem. The BT Call Guardian and the answering machine now work without any unusual noises on hang-up and it disconnects cleanly and immediately. Thank you for that suggestion.

The existing batteries in the first two BT8500 handsets were fine - I had replaced them less than a year ago with a set of known branded ones so they ought to have been. The set in the third handset had not been replaced because it was still working "OK" at the time and I didn't have sufficient new ones. I had intended to buy some more and replace them, but over time had forgotten about them. The batteries in that one are no longer holding charge for any length of time so will be replaced once the new batteries arrive.

All in all, I think we have success and a solution for both households so I would like to thank everyone for their helpful and supporting comments.

Edited by TruthDigital (Fri 03-Oct-25 13:37:25)