You have CCTV. Do you still need an alarm?

People ask this a lot, usually after having cameras fitted. The short answer is that cameras and alarms solve different problems, and which you need depends on what you are actually worried about.

What a camera does

A camera records. It gives you evidence afterwards, it lets you check on the property from anywhere, and a visible one is a real deterrent to an opportunist who would rather do the house next door.

What it does not do is make anything happen at the moment somebody is inside. A modern camera with AI detection will send you an alert, and that is genuinely useful, but it is an alert to you, not a response.

What an alarm does

An alarm makes being inside unpleasant and public. A siren going off changes the situation immediately, which is why the majority of alarm activations that are genuine end with somebody leaving quickly.

It also covers the thing cameras cannot: the inside. A camera on the drive says nothing about somebody already through a back window.

When you probably want both

• The property is empty for long stretches, or you travel.
• There is a lot to lose in one room, such as a workshop, a stock room or tools.
• Your insurer asks for an alarm, which many do above a certain sum insured.
• There are multiple ways in and the outside cannot practically all be covered.

When cameras alone are enough

A small terrace with one door, somebody home most of the time and nothing unusual to protect is often fine with cameras and good locks. We will say so. It is not our job to sell you a second system you do not need.

Together they are better than the sum

Where both are on one system, a triggered detector can pull up the camera covering that zone, so the alert on your phone arrives with a picture of what set it off. That is the thing that stops you driving home for a cat. It costs less to do at the same time than to add later.