Monitoring system with movement sensors for intruder alarms adapted to avoid false alarms by means of an alarm free zone

摘要

The system has a series of movement sensors surrounding a monitoring area or an object to be monitored. The detection ranges of the sensors are directed to the area to be secured. The detection ranges of the sensors overlap such that a continuous detection field is formed across the whole area to be monitored. Analysis of the sensor signals is such that an alarm is only output when at least two directly adjacent sensors respond within a given time window, such that a zone results between the sensors in which no alarm is triggered. By varying the spacing, detection angle and alignment of sensors, the extent of the alarm free zone and the alarm zone can be adjusted.