Alarm Systems and Sensors

---

Alarm System

Alarm system is a physical intrusion detection and warning that can use circuit, motion, proximity, and duress triggers.

• are both a detective and deterrent control
  • notify of incident
  • discourage unauthorized access
• often integrated with physical security controls
  • e.g.,
    • cameras, motion sensors
• can sound an alarm or link to a monitoring system
• often linked directly to local law enforcement or third-party security
• can also be silent alarm that only alerts security

Types

• circuit
  • Uses a circuit-based alarm that sounds when the circuit is opened or closed, depending on the type of alarm
  • e.g., door or window opening or by a fence being cut
  • closed-circuit alarm is more secure
    • cannot be defeated by cutting the circuit like an open-circuit alarm
  • suited for use at perimeter and on windows and doors
• motion detection
  • Alarm system triggered by movement as detected by microwave radio reflection or passive infrared sensors
  • Uses a motion-based alarm linked to a detector that is triggered by any movement within an area
  • sensors in these detectors are either:
    • microwave radio reflection
      • similar to radar
    • passive infrared (PIR)
      • detect moving heat sources
  • useful for controlling access to spaces not normally used
• noise detection
  • Uses an alarm triggered by sounds picked up by a microphone
  • AI-backed analysis and identification of specific types of sound can render this type of system less prone to false positives
• proximity
  • Uses RFID tags and readers to track the movement of tagged objects within an area
  • allows system to detect whether someone is trying to remove equipment
• duress
  • Uses an alarm triggered manually by staff if they come under threat
  • many ways to implement
    • wireless pendants
    • concealed sensors or triggers
    • DECT handsets or smartphones
  • some electronic locks can be programmed with a duress code
    • a different code from the access code
    • will open the gateway, but also alert security personnel
  • useful for exposed staff in public areas

Sensor Types

Sensors are a component in an alarm system that identifies unauthorized entry via infrared-, ultrasonic-, microwave-, or pressure-based detection of thermal changes or movement.

• provide proactive detection and alerting
• types
  • infrared sensors
    • detect changes in heat patterns caused by moving objects
    • used in residential and commercial security systems, triggering alarms or activating security lights when detecting motion
  • pressure sensors
    • typically installed inside floors or mats and are activated by weight
    • used in high-security areas to detect unauthorized access
      • or in retail environments to count foot traffic
  • microwave sensors
    • emit microwave pulses and measure the reflection off a moving object
    • often combined with infrared detectors in dual-technology motion sensors
    • less likely to trigger false alarms
      • infrared and microwave sensors must be tripped simultaneously
    • useful in securing large outdoor areas
  • ultrasonic sensors
    • emit sound waves at frequencies above the range of human hearing and measure the time it takes for the waves to return after hitting an object
    • often used in automated lighting systems
      • to switch lights on when someone enters a room
      • switch them off again when the room is empty
  • capacitance sensors
    • monitor the electromagnetic field in a monitored area, sensing disturbances that correspond to motion