Intruder Alarms

Intruder Alarms

Welcome to the latest blog in the Business Security Guide series. In case you missed it, the last blog, all about CCTV, can be read here.

Protecting your business is important to any business owner but getting it right can be tricky. According to the latest crime report, England and Wales have seen a 9% increase in break ins, despite a drop in the overall level of crime. This means that businesses are not getting it right. Installing and maintaining a correctly fitted intruder alarm will reduce the likelyhood of your business falling victim to criminal activity.

In this blog, about intruder alarms, we cover what an intruder alarm is, the types and grades of intruder alarms, integration with CCTV and lastly give some tips on using an intruder alarm effectively.

I hope you find it useful.

What is an Intruder Alarm?

The basic principle of an intruder alarm (or building intrusion detection systems) is to alert you to any unauthorised intrusion into your business.

The most basic alarm will monitor and detect any unauthorised access, or attempted access, into your business once it has been secured. However, with technology, the ability of the intrusion detection system has grown. The system can now monitor and detect if a static object is moved or accessed without authorisation, or if a portable object is leaving a designated area or leaving the building with an unauthorised user. There are sophisticated systems that can use the building’s WIFI and can even extend their range outside of the building.

Despite this, all intruder alarm systems should conform to the basic principle. Well fitted and maintained intruder alarms will make organisations less likely to become victims of crime.

Types of Intruder Alarms

There are several types of intruder alarm and selection will depend on your personal preference, the size of your business, the location, the level of protection you require and so on.

Alarms can be wired or wireless. Wireless alarms are easier to install but are not as reliable, while wired alarms can be disruptive to install. Whether it is a wired alarm or wireless alarm, it is always advisable to get a qualified engineer to fit one correctly.

Alarms can be ‘bells only’, ‘speech dialler’ or a monitored alarm.

A ‘bells only’ alarm makes a loud noise when they are triggered, in the hope to alert a nearby member of the public or scare the intruder off. Unlike the ‘speech dialler’ or monitored alarm, there is no guarantee that anyone will react to the alarm activation. Modern criminals are well aware of this and have been known to activate an alarm and watch to see if there is any form of response before continuing their criminal activity.

A ‘speech dialler’ alarm or ‘text alert’ system will notify a key holder by phone or text. The nominated key holder can respond to the alarm in person or notify another person nearby. With the proliferation of IP CCTV cameras, key holders often ‘dial in’ to the CCTV system to ascertain the cause. Although, this is a better solution then just ‘bells only’ it doesn’t guarantee the property is secure.

An alarm system can also be monitored where an alarm receiving centre (ARC) is notified in the event of an alert. Usually, the ARC will contact the property and ask any respondent for their password. If the password is not correct or no one answers, they will inform the nominated key holder and, in some circumstances, notify the Police. For commercial premises, is this the best solution as it guarantees a response if an alarm is triggered.

Grades of Alarms

In 1997 the European Standards Organisation published EN 50131-1 which introduced security system grading. These standards can be difficult to understand, so I will try and be brief.

The security grade of an alarm is a measure of the resilience to outside influences and to attack by criminals. The grade of the alarm system that you use can be dictated by your insurance company or be determined by a risk assessment.

There are 4 grades of alarm:

Grade 1: For use on low risk domestic properties. Most grade 1 alarms are DIY alarms, often wireless. Any intruders are expected to have little or no expertise. Insurers have been known not to accept this as an adequate level of protection.

Grade 2: This alarm is suitable for higher risk domestic properties or low risk commercial buildings. Grade 2 alarms are the minimum standard required for monitored alarms and as such are the minimum installed by security companies. Any intruders are expected to have more knowledge and some specialist equipment with them.

Grade 3: The alarm is suitable for high risk domestic properties or medium risk commercial buildings. Intruders will have both comprehensive knowledge and portable electronic equipment.

Grade 4: Designed for very high risk properties, in fact, Grade 4 systems are non-existent for practical purposes. There is little alarm equipment available for Grade 4 systems and therefore alarm installers will use some Grade 3 equipment. In which case the official Grade of the whole alarm system is that of the lowest graded piece of equipment used within it.

Apart from increasing control panel event memories and levels of recommended detection, the key difference between Grades 2, 3 and 4 is that movement sensors at Grade 3 must be able to detect masking, i.e. something being placed over the sensor lens. At Grade 4 movement sensors should be able to detect range reduction, i.e. something blocking part of the detectors field of view.

Tips on Using an Intruder Alarm Effectively


Before you install any form of intrusion detection system you should split your business into compartments. Each compartment can be selected by business function or by geographical area. But it is worth considering what each area of your business is used for and who needs access to it.

Shell Protection.

Shell protection, in this instance, is not the shell of the building but rather the shell of each compartment within your business. You should install sensors around each compartment that will notify you if someone breaks in or attempts to break in. Ideally, sensors should cover all vulnerabilities and likely points of entry into each compartment.

Layered and In-Depth Approach

A key aspect to good security is using a layered or in-depth approach. This means, not relying on a single security measure to protect an area or compartment. When looking to protect a compartment consider the potential route of any intruder, you should try and ensure that an attacker will trigger more that one detector.

Use Different Types of Sensor

The most common form of sensor used is the magnetic door sensor, which will activate when the two magnets are separated. However, for best effect it is advisable to use a mixture of sensors such as Passive InfraRed sensors (PIRs), which will detect unusual energy in a monitored space, vibration sensors or infrared beams.

Integration with CCTV

Using CCTV as a primary means of protection against an intruder is a mistake, a more effective way is to use it to support your intrusion detection system. Used correctly, a CCTV camera should be sited in such a way that in the event of an intruder alarm activation, the CCTV system can be ‘dialled into’ remotely to ascertain the cause. If anything nefarious is identified, a speedy and appropriate response can be directed.

Protecting your business can be a challenge but getting the basics right is the first step. An intrusion detection system is a basic security measure that, installed correctly, can greatly improve the effectiveness of your overall security plan and ultimately save you time and money.

If you would like to know more or need help securing your business, then please do get in touch, we are more than happy to help.


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