CST Intrusion Detection & Monitoring 3 — Questions and Answers
Question 1: A seismic sensor installed on a safe would primarily detect which type of intrusion attempt?
- Motion in the surrounding room
- Vibrations caused by drilling or cutting on the protected object (Correct answer)
- Glass breakage in the vicinity
- Electromagnetic field changes near the safe
Correct answer: Vibrations caused by drilling or cutting on the protected object
Seismic sensors are tuned to detect low-frequency vibrations transmitted through solid objects, making them ideal for detecting physical attacks such as drilling or grinding on safes or vaults.
Question 2: In a monitored alarm system, what is the standard communication path used as a primary channel under UL 2050 requirements?
- Cellular-only transmission
- Internet (IP) transmission
- Digital communicator over PSTN (Correct answer)
- Radio frequency (RF) transmission
Correct answer: Digital communicator over PSTN
UL 2050 traditionally recognizes the digital communicator over the Public Switched Telephone Network (PSTN) as the primary communication path, though IP and cellular are now widely used as supplements or replacements.
Question 3: What is the function of an alarm control panel's 'event log' or 'history buffer'?
- To store encrypted user PINs
- To record a time-stamped sequence of system events for review and audit (Correct answer)
- To queue alarm signals for transmission during communication failures
- To log maintenance schedules
Correct answer: To record a time-stamped sequence of system events for review and audit
The event log maintains a time-stamped record of alarms, arm/disarm actions, faults, and user activity, which is critical for post-incident investigation and system auditing.
Question 4: Which wiring configuration is required to ensure a contact device reports both an alarm condition AND a tamper condition on a single two-wire circuit?
- Normally open (NO) contact only
- Normally closed (NC) contact with end-of-line resistor
- Double-balanced circuit with two resistors (Correct answer)
- Four-wire supervised loop
Correct answer: Double-balanced circuit with two resistors
A double-balanced circuit uses two resistors—one in series and one in parallel—to create three distinct resistance states: normal, alarm, and tamper/short.
Question 5: A customer reports that their outdoor microwave motion detector triggers frequently when no one is present. Which environmental factor is most likely responsible?
- Low ambient temperature
- Vegetation movement caused by wind (Correct answer)
- High relative humidity
- Direct sunlight on the detector housing
Correct answer: Vegetation movement caused by wind
Microwave sensors detect motion by measuring Doppler shift in reflected RF energy; moving vegetation such as tree branches or tall grass falls within their detection pattern and causes false alarms.
Question 6: Under the UL 681 standard for installation of burglar and holdup alarm systems, what minimum wire gauge is typically required for detection circuit wiring?
- 22 AWG (Correct answer)
- 18 AWG
- 16 AWG
- 14 AWG
Correct answer: 22 AWG
UL 681 generally specifies a minimum of 22 AWG conductors for detection (zone) wiring in burglar alarm installations.
Question 7: What distinguishes a 'holdup' alarm from a standard 'burglary' alarm in a commercial intrusion detection system?
- Holdup alarms use wireless sensors; burglary alarms use wired sensors
- Holdup alarms are triggered covertly by occupants under duress; burglary alarms detect unauthorized entry (Correct answer)
- Holdup alarms require police response; burglary alarms notify a guard service
- Holdup alarms are always silent; burglary alarms always sound audibly
Correct answer: Holdup alarms are triggered covertly by occupants under duress; burglary alarms detect unauthorized entry
Holdup (panic) alarms are activated covertly by employees when threatened by robbery, while burglary alarms respond automatically to unauthorized intrusion attempts.
CST Intrusion Detection & Monitoring 3
A seismic sensor installed on a safe would primarily detect which type of intrusion attempt?