Motion sensor
A device that detects movement in an area is where they shouldn’t be (eg, an intruder) and sends an alert to your control panel, which alerts your monitoring centre.
Monitored alarm system
A monitored system alarm will alert a call centre if the alarm gets triggered and this call centre will contact the police.
Unmonitored alarm system
This system sets off a loud siren inside and outside the house when the alarm is tripped. This system relies on your neighbours nearby to call the police if you are not home.
Window and door sensors
Door and window sensors will sound an alarm (emit a siren, trigger your home security system or sending you an alert on your phone) when someone picks a lock or climbs through an open window or door.