How does the phone network switch-off affect my alarm?

The UK's analogue phone network is being retired and replaced with digital voice over broadband, which means alarms that signal over a traditional phone line stop working reliably. If your monitored alarm uses a landline, it needs migrating to broadband or mobile signalling — this does not happen automatically, and a failed path is silent.

The old analogue network, the PSTN, carried its own power and stayed up when the mains failed. Digital voice does not: it runs over your broadband router, so it goes down when the power or the internet does. An alarm that dials out over a line like that has a much weaker path than it used to.

Some older alarm communicators also simply do not work over digital voice, because they expect analogue signalling tones. In those cases the alarm can appear entirely normal while being unable to reach the ARC.

The switch-off has been rescheduled more than once, and communications providers are migrating customers in batches, so the date that matters is the one your own provider gives you for your line. Do not rely on a national date.

The action is the same either way: ask your alarm monitoring provider to confirm in writing what your system signals over now, and whether it is affected. If it is, the fix is normally a new communicator using broadband, mobile, or both.