CAT CAT Electrical and Wiring Fundamentals 2 — Questions and Answers
Question 1: What voltage level is most commonly used for residential security alarm control panels?
- 12V DC (Correct answer)
- 120V AC
- 24V AC
- 48V DC
Correct answer: 12V DC
Most residential alarm panels operate on 12V DC supplied by a plug-in transformer and backed up by a 12V sealed lead-acid battery.
Question 2: What is a 'home run' wiring method in alarm installations?
- Each device is wired directly back to the panel with its own dedicated wire run (Correct answer)
- All devices share a single continuous wire loop
- Devices are wired in series from one end
- Wiring is routed through the attic only
Correct answer: Each device is wired directly back to the panel with its own dedicated wire run
A home run configuration gives each zone or device its own dedicated wire back to the panel, making troubleshooting and zoning simpler.
Question 3: What causes voltage drop in long alarm wiring runs?
- Wire resistance increases with length, reducing voltage at the device (Correct answer)
- Thicker wire absorbs more current
- Alarm panels automatically limit voltage at 50 feet
- High-frequency signals only travel short distances
Correct answer: Wire resistance increases with length, reducing voltage at the device
Longer wire runs have more resistance, which causes a measurable voltage drop that can prevent sensors or keypads from operating correctly.
Question 4: Which battery chemistry is most commonly used for alarm system standby power backup?
- Sealed lead-acid (SLA) (Correct answer)
- Lithium-ion
- Nickel-cadmium
- Alkaline
Correct answer: Sealed lead-acid (SLA)
Sealed lead-acid batteries are the industry standard for alarm backup power due to their reliability, cost, and compatibility with trickle-charging circuits.
Question 5: What is the function of a tamper switch on an alarm device or enclosure?
- Trigger an alert if the device cover is removed or the enclosure is opened (Correct answer)
- Silence the siren during testing
- Reset the zone after an alarm
- Supervise battery voltage
Correct answer: Trigger an alert if the device cover is removed or the enclosure is opened
Tamper switches detect unauthorized physical access to alarm devices or panels and send a tamper signal to the monitoring center.
Question 6: What is the minimum wire size permitted for power-limited fire alarm circuits under NFPA 70 (NEC)?
- 26 AWG (Correct answer)
- 12 AWG
- 18 AWG
- 10 AWG
Correct answer: 26 AWG
NEC Article 760 permits power-limited fire alarm (PLFA) circuits to use wire as small as 26 AWG, though 18–22 AWG is typical in practice.
CAT CAT Electrical and Wiring Fundamentals 2
What voltage level is most commonly used for residential security alarm control panels?