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Alarm Systems and Sensors

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Summary

PDF p.213

Alarms are crucial in physical security, serving as both detective and deterrent controls. They alert security personnel and building occupants of potential threats or breaches and are often integrated with other security controls like access systems, cameras, and motion sensors.

In plain words

Supplementary — not from your PDF

Alarms are detective and deterrent controls. Circuit alarms trigger when doors or windows open (closed-circuit designs are harder to defeat). Motion alarms use infrared or microwave sensors. Noise alarms use microphones. Proximity alarms track RFID-tagged equipment. Duress alarms are triggered by staff under threat. Sensors include infrared (heat), pressure (weight), microwave (reflections; dual-technology reduces false alarms) and ultrasonic (sound echoes).

Detailed explanation

PDF p.213
  • Types of Alarms
    • Circuit Alarms
      • Definition: Sound when a circuit is opened or closed.
      • Examples: Door/window opening, fence being cut.
      • Closed-Circuit: More secure, cannot be defeated by cutting the circuit.
    • Motion Detection Alarms
      • Definition: Triggered by movement within an area.
      • Sensors: Microwave radio reflection, passive infrared (PIR).
    • Noise Detection Alarms
      • Definition: Triggered by sounds picked up by a microphone.
      • Modern Systems: Use AI to reduce false positives.
    • Proximity Alarms
      • Definition: Use RFID tags and readers to track movement of tagged objects.
      • Purpose: Detect removal of equipment.
    • Duress Alarms
      • Definition: Manually triggered by staff under threat.
      • Implementation: Wireless pendants, concealed sensors, DECT handsets, smartphones, duress codes in electronic locks.
  • Applications of Alarms
    • Perimeter Security: Circuit-based alarms for windows and doors.
    • Access Control: Motion detectors for unused spaces.
    • Public Areas: Duress alarms for exposed staff.
    • Monitoring Systems: Alarms linked to local law enforcement or security companies.
    • Silent Alarms: Alert security personnel without audible sound.
  • Sensor Types
    • Infrared Sensors
      • Definition: Detect changes in heat patterns.
      • Applications: Motion detection in residential and commercial systems.
    • Pressure Sensors
      • Definition: Activated by weight.
      • Applications: High-security areas, retail environments.
    • Microwave Sensors
      • Definition: Emit microwave pulses and measure reflections.
      • Dual-Technology: Combined with infrared detectors to reduce false alarms.
      • Applications: Large outdoor areas like parking lots.
    • Ultrasonic Sensors
      • Definition: Emit sound waves and measure return time.
      • Applications: Automated lighting systems.

Important terms

taken from the text above
Circuit Alarms
Sound when a circuit is opened or closed.
Closed-Circuit
More secure, cannot be defeated by cutting the circuit.
Motion Detection Alarms
Triggered by movement within an area.
Sensors
Microwave radio reflection, passive infrared (PIR).
Noise Detection Alarms
Triggered by sounds picked up by a microphone.
Modern Systems
Use AI to reduce false positives.
Proximity Alarms
Use RFID tags and readers to track movement of tagged objects.
Duress Alarms
Manually triggered by staff under threat.
Perimeter Security
Circuit-based alarms for windows and doors.
Access Control
Motion detectors for unused spaces.
Public Areas
Duress alarms for exposed staff.
Monitoring Systems
Alarms linked to local law enforcement or security companies.
Silent Alarms
Alert security personnel without audible sound.
Infrared Sensors
Detect changes in heat patterns.
Pressure Sensors
Activated by weight.
Microwave Sensors
Emit microwave pulses and measure reflections.
Dual-Technology
Combined with infrared detectors to reduce false alarms.
Ultrasonic Sensors
Emit sound waves and measure return time.

Examples & real-world scenarios

Supplementary — not from your PDF
  • A door contact that alarms when opened after hours.
  • An RFID proximity alarm when a tagged laptop leaves the building.
  • A silent duress button at a bank counter.

Scenario

An outdoor car park's motion sensors keep false-alarming in bad weather. Dual-technology sensors (microwave plus infrared) must both trigger, which reduces false alarms.

Common mistakes

Supplementary — not from your PDF
  • Mixing up proximity alarms (tracking tagged objects) and motion alarms.
  • Forgetting silent alarms, which alert security without warning the intruder.

Practical skills

Supplementary — not from your PDF
  • Pick an alarm and sensor type for a given area.

What I should remember

Key Points PDF p.213
  • Types of Alarms
    • Circuit: Door/window opening, fence cutting.
    • Motion Detection: Movement within an area.
    • Noise Detection: Sounds picked up by a microphone.
    • Proximity: RFID tags and readers.
    • Duress: Manually triggered by staff.
  • Applications of Alarms
    • Perimeter Security: Windows, doors.
    • Access Control: Unused spaces.
    • Public Areas: Exposed staff.
    • Monitoring Systems: Linked to law enforcement.
    • Silent Alarms: Non-audible alerts.
  • Sensor Types
    • Infrared: Heat pattern changes.
    • Pressure: Activated by weight.
    • Microwave: Pulse reflections.
    • Ultrasonic: Sound wave return time.