CST Intrusion Detection & Monitoring 2 — Questions and Answers
Question 1: Which type of motion sensor is best suited for detecting intruders in environments with large temperature fluctuations?
- Passive Infrared (PIR)
- Microwave
- Dual-technology (PIR + microwave) (Correct answer)
- Ultrasonic
Correct answer: Dual-technology (PIR + microwave)
Dual-technology sensors combine PIR and microwave detection, reducing false alarms caused by temperature changes that would trigger a PIR-only sensor.
Question 2: In intrusion detection systems, what does the term 'cross-zoning' refer to?
- Wiring sensors across multiple panels
- Requiring two separate zones to alarm before triggering a response (Correct answer)
- Dividing a facility into geographic sectors
- Connecting zones from different buildings
Correct answer: Requiring two separate zones to alarm before triggering a response
Cross-zoning requires activation of two independent detection zones to confirm an intrusion before generating an alarm, significantly reducing false alarm rates.
Question 3: A glass break detector set to 'wideband' mode will respond to which frequency range?
- Only low-frequency flex sounds
- Only high-frequency shattering sounds
- Both flex and shatter frequencies (Correct answer)
- Only ultrasonic frequencies above 20 kHz
Correct answer: Both flex and shatter frequencies
Wideband glass break detectors monitor both the low-frequency flex sound and the high-frequency shatter sound to confirm actual glass breakage.
Question 4: What is the primary purpose of a 'supervised' intrusion detection circuit?
- To monitor operator login activity
- To continuously verify circuit integrity and detect tampering or wiring faults (Correct answer)
- To supervise guard patrol routes
- To log all entry and exit events
Correct answer: To continuously verify circuit integrity and detect tampering or wiring faults
Supervised circuits use end-of-line resistors or active polling to detect open or short circuit conditions, indicating tampering, cut wires, or equipment failure.
Question 5: During system commissioning, a PIR detector repeatedly triggers false alarms near a south-facing window. The most likely cause is:
- Insufficient detection range
- Thermal masking from sunlight heating the detection zone (Correct answer)
- Incorrect wiring polarity
- A faulty tamper switch
Correct answer: Thermal masking from sunlight heating the detection zone
Direct sunlight can heat surfaces within the PIR's detection pattern, creating thermal gradients that mimic body heat and trigger false alarms.
Question 6: An active infrared beam detector generates a fault condition when the receiver signal drops by what typical threshold percentage?
- 10%
- 25% (Correct answer)
- 50%
- 75%
Correct answer: 25%
Most active IR beam detectors are engineered to alarm when received signal strength drops by approximately 25%, balancing sensitivity with immunity to minor obstructions like fog or insects.
Question 7: Which intrusion detection standard governs the grading of alarm systems for residential and commercial applications in the United States?
- UL 681
- UL 2050
- IEC 60839
- ANSI/SIA CP-01 (Correct answer)
Correct answer: ANSI/SIA CP-01
ANSI/SIA CP-01 is the Control Panel Standard that defines false alarm reduction features and grading criteria widely adopted by AHJs across the United States.
CST Intrusion Detection & Monitoring 2
Which type of motion sensor is best suited for detecting intruders in environments with large temperature fluctuations?