Will My Alarm System Still Work After the PSTN Switch Off?

Will my alarm work after the PSTN switch off?

If your alarm signals out over a traditional phone line and has no other route, it will not work after the PSTN switch off. Once the line is withdrawn the panel has no way to reach the monitoring centre, even though the alarm itself still powers on and sounds locally.

If your alarm already signals over broadband or a mobile connection, it keeps working. The way to find out which you have is to ask your alarm installer or monitoring provider what signalling path is fitted — it takes one phone call and it is the single most important check before your lines are migrated.

Why alarms are affected at all

An alarm panel that dials out over a traditional phone line is using the same network as your voice calls. When that line is withdrawn, the panel loses the route it uses to reach the monitoring centre.

The same applies to telecare and personal alarm units, lift emergency lines, door entry systems and gate intercoms. Anything with a cable running to a phone socket needs checking, not just the handsets on the desks.

Single-path versus dual-path signalling

Single-path signalling means the alarm has one way of getting a signal out — very often the PSTN line. If that connection is unavailable, the alarm cannot report. Once the line is withdrawn permanently, a single-path PSTN alarm stops working entirely.

Dual-path signalling uses two independent routes, typically a broadband IP connection plus a mobile network path. If one route is disrupted, the other carries the signal. That redundancy is the reason dual-path is the usual recommendation when replacing PSTN-based signalling.

• Single-path PSTN: stops working when the line is withdrawn
• Single-path IP: works, but depends on one connection staying up
• Dual-path IP plus mobile: continues signalling if one path fails

Check with your alarm provider before you migrate

Compatibility varies a lot by panel age and model. Some panels can be upgraded with an IP or mobile communicator module; older ones need replacing. Some insurers and monitoring contracts also specify a signalling grade, which affects what you're allowed to fit.

Your alarm installer or monitoring provider is the right authority on that, and they need notice. Contact them before the migration date is booked, not after.

You can phase it site by site

If you have several premises, migration does not have to happen everywhere at once. Sites can be moved in sequence, so you can start with the simplest location, confirm the alarm signalling works as expected, and then apply the same approach elsewhere.

Phasing also spreads the cost of any communicator upgrades across a longer period, which is usually easier to budget for.

How we handle connected equipment

Before we schedule anything, we go through what is actually plugged into your lines — alarms, lifts, intercoms, card machines and any legacy modem or fax. Card terminals and EPOS have their own considerations, which we cover separately.

Each item gets an owner and an action: upgrade, replace or confirmed unaffected. The migration is only booked once that list is clear, so nothing is discovered on the day the old line goes.