Intruder Alarm Monitoring Services
A monitored intruder alarm does more than make a noise. When it activates, a signal goes to an alarm receiving centre, where an operator follows a plan agreed in advance: checking whether the activation is genuine, calling your keyholders, sending a response officer and, where the system qualifies, asking the police to attend.
This page explains how monitored intruder alarms work, what the police need before they will respond, what alarm grades mean and how our keyholding and alarm response fits in. For fire and building systems, see our alarm monitoring services overview.
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How a Monitored Intruder Alarm Works
Detectors on your premises, such as movement sensors, door contacts and shock sensors, are wired or wirelessly linked to a control panel. When the system is set and a detector is triggered, the panel sends a signal to the alarm receiving centre (ARC), usually over an internet connection with a mobile or radio path as backup.
The operator sees which zone was triggered and when. Depending on how the system is set up, one activation on its own may be treated as unconfirmed, while a second detector in a different zone, or images or sound from the site, confirm that an intrusion is likely. The operator then works through your response plan.
- Signal received and logged at the alarm receiving centre
- Activation checked against other zones, video or audio where fitted
- Keyholders contacted in the order you choose
- A response officer sent to attend, if agreed
- Police asked to attend confirmed alarms on systems with a URN
Keyholding and alarm response from SIA-licensed officers
Police Response and Your URN
The police do not respond to every alarm. Under the National Police Chiefs' Council (NPCC) policy on security systems, a monitored intruder alarm needs a Unique Reference Number (URN) from your local police force before its alarm calls are passed to them. As general guidance:
- The system must be installed and maintained by a company certified by an inspectorate the police recognise, such as the NSI or SSAIB, to the relevant British and European standards.
- It must be monitored by an alarm receiving centre that meets the required standards.
- You need at least two trained keyholders, or a keyholding company, who can attend within the time the police set, normally 20 minutes.
- Only confirmed alarms are normally passed to the police, which is why confirmation technology matters.
- Too many false alarms in a 12-month period can lead to police response being withdrawn until the cause is fixed.
Your installer applies for the URN on your behalf. If you are not sure whether your system has one, ask your installer or alarm company.
Keyholding and Alarm Response
Most activations happen when nobody is on site, and someone has to attend. Without a keyholding service that usually means a manager getting a call at night, driving in alone and walking into a building that may have been broken into.
With our keyholding and alarm response service, your keys are stored securely and an SIA-licensed officer attends instead. The officer searches for signs of intrusion, secures the premises before leaving, arranges emergency repairs if they are needed and sends you an incident report with photographs. The police accept a keyholding company in place of staff keyholders, provided it can meet their attendance requirements.
For sites that also need a visible presence, alarm response can be combined with mobile patrols.
Guidance for buyers
Alarm Grades Explained: BS EN 50131
BS EN 50131 is the European standard for intruder and hold-up alarm systems, applied in the UK together with PD 6662. It sets four security grades based on the risk at the premises and how capable an intruder is likely to be. Your insurer will often say which grade they expect.
Grade 1
Low risk. Assumes an intruder with little knowledge of alarm systems. Rarely suitable for commercial premises.
Grade 2
Low to medium risk. Assumes some knowledge of alarm systems and a limited range of tools. Common in homes and lower-risk premises such as small offices.
Grade 3
Medium to high risk. Assumes an intruder who knows alarm systems and has a full range of tools and portable electronic equipment. Typical for commercial premises with valuable stock, cash or equipment.
Grade 4
High risk. Assumes a well-resourced intruder able to plan an attack in detail. Used for high-security sites such as banks, jewellers and some government premises.
Keeping False Alarms Down
False alarms cost money, annoy neighbours and can put police response at risk. Most can be avoided:
- Keep the system serviced at the intervals your installer and insurer require.
- Make sure everyone who sets and unsets the alarm is trained, and remove codes for people who leave.
- Check that detectors are not set off by heaters, blinds, stacked stock or pests.
- Ask about confirmation technology, so one faulty detector does not lead to a police call.
- Review the log after every activation and fix the cause.
Choosing an Alarm Monitoring Provider
Questions worth asking any provider:
- Which alarm receiving centre monitors the system, and which standards is it certified to?
- Is the installer certified by the NSI or SSAIB, so the system can hold a URN?
- Who attends when the alarm goes off, and do they hold an SIA licence?
- How will you be told about activations, and what reports will you get?
- What happens if the signalling path fails?
Frequently Asked Questions
Common questions about monitored intruder alarms.
What is a URN and do I need one?
A Unique Reference Number is issued by your local police force to a monitored alarm that meets the NPCC policy on security systems. Without one, the alarm receiving centre cannot pass your alarm calls to the police. Your installer applies for it, and it can be withdrawn if the system has too many false alarms.
Will the police attend every time my alarm goes off?
No. The police normally respond only to confirmed alarms from systems with a URN, and attendance depends on other demands at the time. That is why most businesses also arrange keyholding, so someone always attends.
What grade of intruder alarm does my business need?
It depends on your risk and your insurer. Grade 2 suits many lower-risk premises, while Grade 3 is typical for commercial sites with valuable stock or equipment. Your installer should carry out a risk assessment and your insurer may set a minimum grade.
What happens when my alarm goes off at night?
The alarm receiving centre receives the signal and follows your response plan. With our keyholding service, an SIA-licensed officer attends with your keys, checks the premises, secures them before leaving and reports back to you.
What is the difference between a bells-only alarm and a monitored alarm?
A bells-only alarm sounds a siren on site and relies on someone nearby to act. A monitored alarm sends a signal to an alarm receiving centre, so keyholders are called and, on systems with a URN, the police can be asked to attend.
Can my cameras be linked to the intruder alarm?
Yes. Linking CCTV lets operators look at the area where the alarm was triggered and confirm whether there is an intruder. See our CCTV monitoring services.
Talk to Us About Alarm Response
Tell us about your premises and your current alarm system, and we will explain how keyholding and alarm response would work for your site. Quotes are free and itemised.