Intruder alarm or CCTV: what each does for a business, and how they work together

An intruder alarm reacts. CCTV records. An alarm makes a noise or sends a message the moment a sensor trips, but it cannot tell you who or what set it off. CCTV shows you who and what, but on its own it does not tell anyone in time.

If you have only one, the other covers a gap. Alerts from the CCTV cameras you already have can close part of that gap without a new system.

An intruder alarm is built from a few parts. It is normally fitted and serviced by a specialist alarm company.

• Sensors. Door and window contacts, movement detectors inside rooms, and glass-break sensors. They sit at the edge of the protected area, inside it, or both.
• A control panel. You arm it when you leave and disarm it when you come in. It reads the sensors and decides when to raise the alarm.
• A siren or sounder, usually outside, sometimes inside as well.
• A communicator, which sends the alarm over broadband or the mobile network.
• An alarm receiving centre, if the alarm is monitored. Trained staff there assess the signal and may phone your keyholders or the police. Monitoring is optional. An alarm that is not monitored relies on the siren and on messages to the people you list.

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CCTV is cameras, usually a recorder, and a way to watch. It shows what is happening, lets you look at the premises from your phone or a screen, and keeps recorded video as evidence. Visible cameras can also put some people off.

On its own, CCTV does not tell anyone anything. The system records, and you find out when you look. If you are checking what you already have, read business security cameras: check what you have before you buy new ones.

• What it tells you. The alarm: that a sensor was tripped. CCTV: what the camera saw.
• When you find out. The alarm: straight away, if it is set up to tell you. CCTV: when you look, unless alerts are added.
• Who or what it was. The alarm does not know. CCTV shows it.
• Evidence. The alarm leaves a log of times. CCTV leaves video.
• Where it works. An alarm is usually built around the inside of a building. CCTV also covers the yard, the car park and the outside walls.
• Typical false alarms. The alarm: a sensor set badly, or someone forgetting to disarm. CCTV motion alerts: shadows, rain, insects and headlights.

An intruder alarm gives you no picture. A tripped sensor in a store room could be a thief, a cat or a door that did not close. You have to go and look, or phone someone who can. It also only knows about the rooms where sensors are fitted.

CCTV gives you the picture but not the warning. A camera can show a break-in clearly and nobody learns about it until the morning. A camera can also be covered, knocked out of focus or switched off, and a recorder can fail without anyone noticing.

Used together, each one answers the question the other leaves open.

• The alarm trips. You, or the alarm receiving centre, look at the cameras to see whether it is real. This is often called verifying the alarm. Ask your alarm company whether your cameras can be linked to the alarm.
• The cameras cover the yard and the outside of the building, where an indoor alarm cannot reach.
• Camera alerts add a second early warning: a person in a zone you mark, outside your opening hours, with a photo.
• Afterwards you have a log of times from the alarm and video from the cameras to show an insurer or the police.

Some insurers ask for a particular kind of alarm, and what the police do after a call depends on where you are and how the alarm is set up. We do not give rules here. Ask your alarm company and your insurer before you change or remove anything. Camera alerts do not replace an intruder alarm.

If you have CCTV but nothing that tells you when something happens, you do not have to buy a new system to get a warning. Our software installs on a Windows computer at your premises in 60 seconds and reads the video from your cameras and recorder: Hikvision, Dahua, CP Plus, TVT, Uniview, Axis, Hanwha, or any camera or recorder that offers RTSP or ONVIF. Nothing on your existing system changes.

Read more in after-hours alerts from your existing cameras and how to know if someone covered your CCTV camera.

• People in the zones you mark, outside the hours you set, is standard on every site.
• Smoke and fire, a covered camera and a camera that goes offline are standard too.
• Our own AI models, trained in-house, watch every camera. A second, larger model checks each event before you are alerted.
• The alert is a photo with the camera and the time, on WhatsApp, Telegram or the Foreman app.
• It is not an alarm. There is no siren, no call to your keyholders and no call to the police. The people you choose get the photo and decide what to do.