An intruder alarm system detects someone entering or moving about a protected building when they should not be there, and raises the alarm. Depending on the system, that means a siren on site, a message to your phone, a signal to a monitoring centre, or all three.
The parts of a system
- Control panel. The brain of the system. It receives signals from every detector, knows whether the system is armed, and decides when to sound the alarm and who to tell. It is kept in a secure place and has a backup battery.
- Keypad or app. Where you arm and disarm the system and see its status, with a code, a card or a phone.
- Detectors. The sensors that notice an intruder: door and window contacts, movement detectors, glass-break detectors and others.
- Siren and strobe. Sound the alarm to frighten off an intruder and alert people nearby.
- Communicator. Sends the alarm off the premises over the internet or a mobile network, to a monitoring centre or to your phone.
- Power supply and battery. Keep the system running through a power cut.
The detectors, and what each is good for
- Door and window contacts. A magnet and a sensor on the frame. The alarm triggers when the door or window opens. Simple and very reliable for entry points.
- Passive infrared (PIR) movement detectors. Sense the heat of a person moving across their field of view. The most common indoor detector. Pet-tolerant models ignore small animals.
- Dual-technology detectors. Combine PIR with a second method such as microwave, and need both to agree before they alarm. Used where false alarms are a problem, such as warehouses and sunrooms.
- Glass-break detectors. Listen for the sound of breaking glass and cover several windows from one spot.
- Vibration and shock sensors. Fitted to doors, windows, safes or walls to detect attempts to break in.
- Outdoor and beam detectors. Protect yards, driveways and perimeters, from outdoor-rated movement detectors to pairs of beams.
How it works day to day
The system is divided into zones, usually one for each detector or group of detectors. You arm it with a code, card or app when you leave, and an exit delay gives you time to get out. If a detector in an armed zone triggers, the panel starts the alarm. At the main door there is an entry delay, so you can disarm the system before it sounds.
Most systems let you arm part of the building, often called stay or home mode, so you can be inside with the movement detectors off while the doors and windows stay protected. Some zones, such as tamper switches and panic buttons, are active all the time, whether the system is armed or not.
Monitored or not
- Unmonitored (local) alarms. Sound a siren and may send a notification to your phone. They rely on someone nearby to act on it.
- Monitored alarms. Send the alarm signal to a monitoring centre, where an operator follows set procedures, such as calling you and your contacts and arranging a response if needed. Monitoring is normally a subscription.
Wired or wireless
Wired systems use cable to each detector. They are common in new builds and commercial sites, where cable can be run in the walls and ceilings as the building goes up. Wireless systems use battery-powered detectors that talk to the panel by radio, so they suit existing homes and shops where running cable is difficult. Many systems combine both. Wireless detectors need their batteries replaced on schedule.
Avoiding false alarms
- Position detectors away from heaters, air-conditioning vents, direct sunlight and moving curtains.
- Use pet-tolerant detectors if you have pets.
- Make sure everyone who uses the system knows how to arm and disarm it, and what to do if they set it off by mistake.
- Have the system tested and maintained regularly, and replace backup batteries before they fail.
How the alarm reports
Older alarms report over the copper telephone line. As that line is replaced by the NBN and mobile networks, alarm communicators have to move to an internet or mobile path, ideally with a second path as a backup. If your alarm is more than a few years old, check how it sends its signal.
Standards and installation
In Australia, intruder alarm design, installation and maintenance are covered by the standard AS/NZS 2201.1, and installers must hold the licence required in their state or territory. Your insurer may also set requirements for the system. A good design starts with a site assessment: where an intruder would get in, what needs protecting, and how people use the building.
Teracom Solutions supplies and installs intruder alarm systems and offers alarm monitoring. Contact us with a description of your site and we will help you work out what you need.