Intrusion and perimeter detection that people still trust after month three

Indoor intrusion alarms

Intrusion systems combine detectors (dual-technology motion, door and window contacts, glass-break, seismic sensors on safes and walls), a control panel, keypads, and signalling to the people who respond. EN 50131 grades systems from 1 (low risk) to 4 (high risk). The grade drives detector type, tamper protection, signalling path redundancy and how the system resists being defeated. When a client or insurer specifies a grade, we design to it and document how each requirement is met.

Detector placement decides the false-alarm rate. Air-conditioning outlets, sunlight moving across a floor, and stock on high shelving all produce alarms when a motion detector is in the wrong place. The survey records those conditions for each area.

Fibre-optic perimeter fence detection

On long fence lines a sensing fibre cable is attached to the fence fabric. Climbing, cutting or lifting the fence creates vibration that the processor analyses. Two broad approaches exist:

• Zoned systems divide the perimeter into fixed zones and report which zone alarmed. Simple and robust, good for shorter perimeters.
• Distributed (location-resolving) systems locate the disturbance along a continuous cable, so one processor can cover kilometres and point a PTZ camera at the event.

Fence condition matters as much as the sensor. A loose, rattling fence produces alarms in the wind. We inspect and record fence tension, posts, gates and ground clearance during the survey and treat gates as separate zones with their own detection.

Nuisance alarms and verification

Wind, sandstorms, rain, animals and nearby traffic all produce signals. The fix is calibration on site with real conditions, per zone, and an alarm-verification step: each perimeter alarm brings up the camera view of that zone so an operator confirms before anyone is dispatched. We record the calibration settings so a later technician doesn't reset them blindly.