Fire Alarm System

Practice flashcards covering residential alarm system components, intrusion-sensing technologies, life safety (smoke and heat detection), and fire alarm circuit operations.

What are residential alarm systems considered under the CE Code and what is their nominal voltage?

They are considered Class 2 circuits and operate at a nominal voltage from $6\,V$ to $12\,V$.

According to Rule 16-212 1), how far must alarm system conductors be separated from insulated power circuit conductors operating at $300\,V$ or less?

At least $50\,mm$.

What is the purpose of the end-of-line (EOL) resistor in a monitored zone loop?

It allows a small amount of monitoring current to flow back to the control panel to determine if the circuit is complete or tampered with.

Why are sirens often installed in cold air returns or attic spaces?

To make it difficult for an intruder to disable them and to take advantage of the spaces' ability to resonate the sound.

What is a magnetic reed switch and how does it function?

It is a perimeter device consisting of a thin metal reed in a vacuum tube that is pulled closed by the magnetic force of a nearby magnet.

In window screen protection, how far apart should the fine insulated wires be installed?

They are installed in parallel paths about $5\,cm$ to $7\,cm$ apart.

What is the functional difference between an acoustic shock detector and an acoustic sound pattern detector?

An acoustic shock detector senses rapid air pressure changes from breaking glass, while an acoustic sound pattern detector uses a computer chip to listen for the specific frequency pattern of breaking glass.

What are the three LEDs on a dual technology glass break detector used to indicate?

One indicates the acoustic shock detector is activated, the second indicates the sound pattern detector is activated, and the third indicates an alarm signal has been sent to the CPU.

How do Passive Infrared (PIR) detectors sense motion?

They sense changes in heat through a lens at different focus points, referencing the background temperature against moving heat-radiating sources like people.

What is a major disadvantage of microwave motion detectors regarding false alarms?

Unlike PIRs, microwaves can easily pass through materials like glass and cinder block walls, potentially sensing movement outside the protected area.

Which type of smoke detector is more responsive to flaming fires that produce little visible smoke?

The ionization detector.

What type of smoke detector uses light obscuration to detect visible smoke particles?

The photoelectric detector.

According to CE Code Rule 32-200 1) a), what type of branch circuit must a smoke alarm be connected to?

A branch circuit containing lighting, so that if the circuit trips, the lack of lighting will ensure the power is restored.

What is the standard conductor size for hard-wired smoke alarm power and interconnection in a residential dwelling?

At least No. 14 AWG copper.

At what temperatures are fixed-temperature heat detectors commonly set to activate?

$57^\circ C$ or $93^\circ C$.

What is the activation threshold for a rate-of-rise heat detector?

A temperature increase of $9^\circ C$ or more in one minute.

What are the four possible conditions of a fire alarm system?

Normal, Trouble, Alarm, and Supervisory.

In a fire alarm system, what does a 'Supervisory' condition indicate?

A change in condition of a field device in an automatic sprinkler system, such as a tamper switch, that could prevent proper operation.

Why must each conductor in a fire alarm system be independently terminated?

To ensure the electrical supervision circuitry can detect if a terminal or splice is opened, which would interrupt the supervisory current and signal a trouble condition.

How does a Class B fire alarm signal circuit activate the audible devices (bells)?

During an alarm condition, the control panel reverses the polarity of the circuit, allowing current to flow through blocking diodes and energize the bells.