An intruder alarm system and a method of arming an intruder alarm system

摘要

An intruder alarm system for detecting intrusion in premises, comprising a first group of detectors, a second group of detectors, a control unit (12) and input means (22) connected to the control unit (12). The control unit (12) is arranged so that the alarm system can be set in a first armed mode, in which the first group of detectors is armed and the second group of detectors is disarmed, and a second armed mode, in which the first and second groups of detectors are armed. The control unit (12), in the first armed mode, is arranged for triggering an alarm and automatically arming or activating the second group of detectors when a detector of said first group of detectors is triggered.