ABAT ABAT Sensors, Detectors & Detection Devices 1 — Questions and Answers
Question 1: What type of motion detector uses both microwave and passive infrared technology to reduce false alarms?
- Dual-technology (dual-tech) detector (Correct answer)
- Ultrasonic motion detector
- Photoelectric beam detector
- Vibration sensor
Correct answer: Dual-technology (dual-tech) detector
Dual-technology detectors require both the PIR and microwave sensing channels to trigger simultaneously, dramatically reducing false alarms caused by environmental factors that might fool a single-technology sensor.
Question 2: A passive infrared (PIR) detector senses motion by detecting changes in which physical property?
- Sound wave reflections
- Infrared radiation emitted by moving objects (Correct answer)
- Microwave signal disturbance
- Visible light interruption
Correct answer: Infrared radiation emitted by moving objects
PIR detectors are passive (they emit nothing) and detect the change in infrared heat energy emitted by a warm body (such as a person) as it moves through the sensor's detection zones.
Question 3: What is the primary advantage of a recessed door contact over a surface-mount door contact?
- Higher magnetic strength for wider door gaps
- Concealed installation that is tamper-resistant and aesthetically cleaner (Correct answer)
- Lower cost per unit
- Compatible with aluminum door frames without modification
Correct answer: Concealed installation that is tamper-resistant and aesthetically cleaner
Recessed door contacts are installed inside drilled holes in the door and frame, making them invisible and much harder for intruders to detect, defeat, or tamper with.
Question 4: Which type of glass break detector analyzes the acoustic frequency profile of breaking glass rather than just sensing vibration?
- Shock/vibration sensor
- Acoustic glass break detector (Correct answer)
- Passive infrared detector
- Foil-on-glass sensor
Correct answer: Acoustic glass break detector
Acoustic glass break detectors use a microphone to analyze the audio spectrum of breaking glass, looking for the specific low-frequency thud followed by high-frequency shatter pattern.
Question 5: A magnetic door contact generates an alarm when the door is opened because the magnet moves away from the reed switch. What is the normal (secured) state of the reed switch contacts?
- Open (normally open / NO)
- Closed (normally closed / NC) (Correct answer)
- Alternating between open and closed
- Floating (high-impedance state)
Correct answer: Closed (normally closed / NC)
Standard alarm door contacts use normally closed (NC) reed switches; when the magnet is close (door shut), the contacts are held closed, and opening the door removes the magnetic field, opening the circuit and triggering an alarm.
Question 6: What is the maximum recommended gap between a magnetic door contact and its corresponding magnet for reliable operation?
- 1/4 inch (6 mm)
- 1/2 inch (12 mm) (Correct answer)
- 3/4 inch (19 mm)
- 1 inch (25 mm)
Correct answer: 1/2 inch (12 mm)
Most standard magnetic door contacts are specified to operate reliably with a gap of up to 1/2 inch (12 mm) between the magnet and the switch body; wider gaps may cause false alarms or missed detections.
ABAT ABAT Sensors, Detectors & Detection Devices 1
What type of motion detector uses both microwave and passive infrared technology to reduce false alarms?