What is a signalling device or alarm communicator?

A signalling device, also called a communicator, is the unit that connects your alarm panel to the Alarm Receiving Centre and transmits activations to it. It is a separate piece of hardware from the alarm panel, and it is usually the only thing that needs adding to make an existing alarm monitorable.

It is the part of the system that determines how signals travel — over broadband, over a mobile network, or both — and how quickly a failed path is detected. Its specification is what EN 50136 categories describe.

Practically, this is good news for anyone with an existing alarm: adding monitoring is often a matter of fitting a communicator to a panel you already own, not replacing the system. Whether that is possible depends on the panel's age and whether it has a suitable output.

The communicator is normally supplied on the monitoring contract, and this is worth reading carefully. Some are supplied outright, some are rented, and some are locked to one ARC. That distinction determines how easily you can change provider later.