Old home alarm system + BT PSTN switch off

Hey all

We have a really old alarm system (25 years+) that uses a RJ11 wire that connects to the BT socket to make an outgoing call if the alarm is triggered (it's got a pre-recorded message that it will read out once the phone is answered).

I think BT has finally got around to switching off the PSTN and that now renders my ability for phone calls to be made.

What are the alternative ways (other than upgrading the alarm panel to the latest) to get this functionality back temporarily? Ideally want some 'retrofitted device' that can I can plug in the RJ11 wire to still make those outgoing calls? Such a thing exist? Or what are the general alternatives?

TIA!

If you wanted to set up a new "line" you can get an Analogue Telephone Adaptor (ATA) which connects to your internet router and provides an RJ11 socket for a traditional phone or your alarm panel.

Either if you have no telephone service anymore, or you have phone service via your router, you probably want to ask this in the VoIP forum as you will get a lot more experience on this than here.
https://forums.thinkbroadband.com/voip.html

25 yo alarm - probably worth upgrading for new functionallity anyway. The communicators now are fully IP based and give you control as well as alerts or warnings.

In reply to a post by jchamier:

If you wanted to set up a new "line" you can get an Analogue Telephone Adaptor (ATA) which connects to your internet router and provides an RJ11 socket for a traditional phone or your alarm panel.
https://forums.thinkbroadband.com/voip.html

The only thing about this is that, the alarm system is so old that even if it was connected (via some adapter or something) it wouldn't know how to make the phone call using the internet. It was literally designed to dial preset phone numbers over an analogue PSTN service.

We moved to a "digital line" from Sky broadband just over a year ago. Our years old PTSN (tone dial) phones now just plug direct into the router and work just the same, even with the same phone number. Vodafone is also similar with their router. This approach may give you a solution, assuming your alarm is tone dial and broadband contract is up for renewal?

Edited by dgilbert2 (Mon 28-Apr-25 21:55:12)

In reply to a post by dgilbert2:

We moved to a "digital line" from Sky broadband just over a year ago. Our years old PTSN (tone dial) phones now just plug direct into the router and work just the same, even with the same phone number. Vodafone is also similar with their router. This approach may give you a solution, assuming your alarm is tone dial and broadband contract is up for renewal?

Interesting. Are your years old PSTN tone dial phones plugging into the router using the BT631A plug? My tone dial phone only has a BT631A plug.

Yes, although the Vodafone router needs a £4 converter cable from RJ11 to BT Telephone Female Socket. All straight forward TBH.

In reply to a post by dgilbert2:

Yes, although the Vodafone router needs a £4 converter cable from RJ11 to BT Telephone Female Socket. All straight forward TBH.

Nice!

I'm convinced it will work now that you've mentioned that. BT has sent be over their SmartHub 2 that does have the BT631A port (phone port) but they charge £3 extra (on top of broadband only option) for the digital voice phone service and digital voice is not supported over non BT supplied routers

I'm looking into a module that attaches into the alarm system to provide cellular notifications / calls if the alarm gets triggered – as a potential solution.

Edited by Bobby_Valentino (Mon 28-Apr-25 22:55:29)

With ancient legacy kit like this, depending on precisely how they operate, there’s usually more to it with compatibility with VoIP analogue telephone adapters and plugging them into the FXS phone port on the back of router.

Not simply just getting an RJ11 to BT adapter of the correct varietal (with or without ring capacitor etc)….

Make sure you thoroughly test and check its sensing line voltage correctly, can successfully dial out and communicate. Also check behaviour on inbound calls, ring detection etc.

Remember that any digital voice / VoIP solution will also need to have local battery backup / UPS to provide a working line during any power outages.

Personally I’d look to upgrade. Most alarm units these days offer native LAN connection through WiFi and/or wired with a 4G backup. In my experience these are not only way more functionality rich than the old phone dialers, they are also far more resilient.

Good luck 🤞