Fixing a broken burglar alarm

Faulty alarms are more than a nuisance

Faulty burglar alarms can be annoying not only to the householder but neighbours and even passers-by. Broken alarms also undermine the effectiveness of security systems as a deterrent again unwanted intruders. Regularly sounding alarms annoy neighbours and promote the notion that a signal is always false and to be ignored rather than acted on.
Many things trigger a false alarm, and much depends on the system and its use. However, engineers from Crown Securities UK are called out to scores of faulty alarms every month and find problems common to many systems.
Knowing how burglar alarm systems are set up and how sensors operate can help understand why a system is not functioning correctly and where any faults are most likely to occur. Most security alarm systems consist of a control box and an array of sensors. The sensors can be of various types and connected to the control box in several ways, but the principle is the same; a controller in the control box runs a computer program that regularly checks the sensors and generates an alarm signal if it detects one or more sensors has been activated.

Common causes of faults

Poor connections are a widespread cause of faulty alarm callouts and can be caused by erosion, improper use, water infiltration and a host of other things. They are usually easy to fix, but the problem is finding them first, especially in large and sophisticated security systems.
Worn-out batteries are another common cause of security system failure. A wireless system, in particular, can be affected by degraded cells, which is a problem with installations that are not regularly checked and maintained. Interference from animals, both domestic pets such as cats and wild animals such as mice or birds, is often behind faults in the security alarm network. It is often the case in units fixed outside or in roof spaces. Degraded sensors are another source of problems for security system engineers, especially if they are poorly sited or badly fitted. Sensors are the 'eyes and ears' of any security alarm system and must be checked regularly and properly maintained.

Use suitable alarm sensors

Sensors are electronic devices that detect movement or sudden changes in light or temperature. Sensors have microswitches which are typically closed but, if the sensors activate, the microswitch opens and the electric circuit is broken. When this happens, the control box automatically triggers the alarm, which may be an external bell, klaxon, or autodialer, and then posts a warning message. Sensors can be of various types. Standard window and door sensors have switches kept closed by a small magnet. Some have shock sensors to detect when glass is smashed or a door is forced. Room sensors have air units that detect body heat. In contrast, microwave sensors are best at detecting movement, and pressure mats are sensitive to someone stepping on them.

How control boxes work

Central control boxes usually have a simple LED display and a keypad for entering commands or inputting passwords. Some control boxes are hard-wired to sensors, while others operate through radio signals or a local wi-fi network. The advantage of wireless control panels is that they can be hidden from view and can't be traced by following wires. Smart security systems can be operated from mobile phones, computers or other devices and don't need a keypad. Control boxes usually operate separate 'zones' that can be controlled independently. For example, zone one might include exterior doors, zone two the downstairs windows, zone three the internal doors, and so on. This way, zones can be automatically switched on and off as needed. External door sensors can be activated at nighttime while internal PIR sensors are turned off so that getting out of bed doesn't trigger an alarm. Security systems for large buildings and commercial properties can have very sophisticated zone alarm networks. Most control boxes will also have tamper circuits to detect unauthorised interference with security systems, even when not active. They will also usually have backup battery power units to cover mains power outages, and external bells or klaxons may also have backup battery power units.

Tamper-proof circuits

Many hard-wired wired alarm networks use a six-core cable. One pair of core wires is used for the sensor circuit, another for the switching system, and the remaining two for the tamper circuit. Microswitches in a tamper circuit usually are closed, allowing the electric current to run. If someone tampers with the system, for example removing a cover or cutting the wire, the switches are thrown, and the circuit is broken.

Calling in the experts

If your security alarm goes off when nothing is wrong, then the sensible thing is to switch it off. The problem is that many alarms are tamper-proof and have backup batteries or built-in systems that override a simple switch-off. After all, if you can turn off the system, then so can an intruder. DIY repairs can also be inadvisable as control panels often operate on mains electricity and messing with the mains without proper knowledge of the system can have shocking results. External bells and sirens may also be connected directly to mains supplies even when they appear inactive. If you have a faulty alarm, especially if it breaks down regularly, we strongly advise you to call the experts to fix it. Crown Securities UK operates a 24-hour emergency callout service every day of the year, even on Bank Holidays, for security alarm systems across the Midlands, North West, North Wales and Manchester. Call us on 01691 623761, and an expert engineer can be with you in under an hour, although time will depend on location. Callers do not need to have a maintenance contract with Crown Securities UK to get help with a broken alarm, and it doesn't matter if someone else installed the system.

More on broken alarm systems

Maintain your burglar alarm system
Broken burglar alarm – Who you gonna call?
Making sense of security alarm sensors