Free Mississippi Alarm Systems and Equipment Practice Questions

Sample Practice Questions

Try these 10 sample questions from the Mississippi Alarm Systems and Equipment practice bank. Each includes the answer and explanation. Continue with the interactive practice above to review the full question set.

1. 1A 12 VDC test source is connected across an isolated 2,000-ohm alarm-loop resistor. Ignoring lead resistance, what current should flow?

   1. A.0.006 mA
   2. B.0.6 mA
   3. C.6 mACorrect answer: C
   4. D.24 mA

   Explanation: DOE Fundamentals Handbook: Electrical Science, Volume 1 states, "Current is equal to the applied voltage divided by the circuit resistance." I = V/R = 12/2,000 = 0.006 A = 6 mA. The other values reflect incorrect metric conversion or multiplication instead of division.

   Reference: DOE Fundamentals Handbook: Electrical Science, Volume 1 — Module 1, p. 14, Ohm's Law

2. 2In an ionization smoke detector, what electrical change is used to recognize particles of combustion entering the sensing chamber?

   1. A.An increase in the chamber's ionization current
   2. B.A decrease in the chamber's ionization currentCorrect answer: B
   3. C.A stable chamber current until a heat threshold is reached
   4. D.A reversal of current direction through the sensing chamber

   Explanation: System Sensor states, "This reduction in the ionized particles results in a decrease in the chamber current" Smoke reduces chamber current. Increasing current reverses the specified effect; waiting for a heat threshold confuses smoke and heat sensing; polarity reversal is not the mechanism.

   Reference: System Sensor: System Smoke Detectors Applications Guide — p. 4, Ionization Smoke Detector Operation

3. 3Which sensing technology is used by the DSC PG9914 motion detector described in its installation instructions?

   1. A.A microwave Doppler transmitter
   2. B.A pyroelectric passive infrared sensorCorrect answer: B
   3. C.An acoustic glass-fracture microphone
   4. D.A magnetic door-contact reed switch

   Explanation: DSC states, "Dual element low-noise pyroelectric sensor." The product is a PIR motion detector. Microwave, acoustic and magnetic devices detect different physical phenomena.

   Reference: DSC PowerG PG9914/PG8914/PG4914 Installation Instructions — p. 2, Specifications, Detector Type

4. 4An alarm device draws 0.25 A from a 24 VDC supply. Its two-conductor cable has 8 ohms of total outgoing-and-return resistance. The device requires at least 22.5 V. What does the loaded-voltage calculation show?

   1. A.22 V reaches the device, below its minimum.Correct answer: A
   2. B.23 V reaches the device, above its minimum.
   3. C.24 V reaches the device, above its minimum.
   4. D.26 V reaches the device, above its minimum.

   Explanation: DOE Fundamentals Handbook: Electrical Science, Volume 1 states, "Applied voltage equals circuit current times the circuit resistance." Cable drop = IR = 0.25 A × 8 ohms = 2 V. Device voltage = 24 − 2 = 22 V, which fails the stated 22.5 V minimum. A 23 V result incorrectly halves the already complete loop resistance; 24 V ignores drop; 26 V adds it.

   Reference: DOE Fundamentals Handbook: Electrical Science, Volume 1 — Module 1, p. 14, Ohm's Law; Module 2, p. 29, IR drops

5. 5How does a spot-type photoelectric light-scattering detector normally recognize smoke?

   1. A.Smoke raises the temperature of a bimetallic strip.
   2. B.Smoke increases current through an ionization chamber.
   3. C.Smoke scatters source light onto a photosensitive element.Correct answer: C
   4. D.Smoke completes a contact between the two supply wires.

   Explanation: System Sensor states, "light strikes the particles (Figure 7) and is scattered onto the photosensitive device causing the detector to respond." The detector responds to scattered light reaching its sensor. Heat sensing, ionization current and contact closure are different initiating mechanisms.

   Reference: System Sensor: System Smoke Detectors Applications Guide — p. 5, Photoelectric Light Scattering Smoke Detector

6. 6A partition would hide part of a room from a PG9914 detector's field of view. What installation choice follows the detector's instructions?

   1. A.Accept the location if the radio placement test shows a strong signal.
   2. B.Accept the location if the control panel allows the zone to be armed.
   3. C.Reposition the detector to keep the required field of view clear.Correct answer: C
   4. D.Increase motion sensitivity without checking the obscured coverage area.

   Explanation: DSC states, "Do not partially or completely obscure the detector's field of view." Radio delivery and zone arming do not establish unobstructed PIR coverage. Increasing sensitivity does not remove the physical obstruction; the detector must be positioned to keep its required field of view clear.

   Reference: DSC PowerG PG9914/PG8914/PG4914 Installation Instructions — p. 1, General guidance

7. 7A regulated alarm accessory draws 0.40 A at 12 VDC. What electrical power does it consume?

   1. A.0.033 W
   2. B.4.8 WCorrect answer: B
   3. C.12.4 W
   4. D.30 W

   Explanation: DOE Fundamentals Handbook: Electrical Science, Volume 1 states, "Power is also described as the current (I) in a circuit times the voltage (E) across the circuit." P = IV = 0.40 × 12 = 4.8 W. Dividing current by voltage gives 0.033, adding gives12.4, and dividing voltage by current gives30; none is power.

   Reference: DOE Fundamentals Handbook: Electrical Science, Volume 1 — Module 1, p. 16, Power

8. 8What change does a projected-beam smoke detector use to detect smoke along its light path?

   1. A.Reduced light reaching the receiving sensorCorrect answer: A
   2. B.Increased light scattered into an off-axis receiving sensor
   3. C.Unchanged received light until smoke heats the transmitter
   4. D.A change in light wavelength rather than received intensity

   Explanation: System Sensor states, "Smoke particles reduce the amount of light reaching the sensor by scattering and absorbing some of the light" Smoke attenuates the transmitted beam. Increased off-axis light describes spot scattering; a temperature threshold or wavelength shift is not the stated beam-obscuration mechanism.

   Reference: System Sensor: System Smoke Detectors Applications Guide — p. 18, Glossary, Projected Beam Smoke Detector

9. 9Which proposed PG9914 mounting location best follows the manufacturer's environmental guidance?

   1. A.A stable indoor wall away from heat sources and draftsCorrect answer: A
   2. B.A wall directly above a space heater in its rising air stream
   3. C.An exterior wall exposed to direct sunlight and rain
   4. D.A flexible curtain support directly beside a supply-air outlet

   Explanation: DSC states, "Keep away from heat sources." The same guidance also says avoid drafts, outdoors and direct sunshine, and use a solid stable surface. The other locations introduce those stated environmental or stability problems.

   Reference: DSC PowerG PG9914/PG8914/PG4914 Installation Instructions — p. 1, General guidance

10. 10Two resistors, 1,000 ohms and 2,200 ohms, are connected in series on an isolated test loop. What total resistance should be measured?

    1. A.688 ohms
    2. B.1,200 ohms
    3. C.2,200 ohms
    4. D.3,200 ohmsCorrect answer: D

    Explanation: DOE Fundamentals Handbook: Electrical Science, Volume 1 states, "The total resistance in a series circuit is equal to the sum of all the parts of that circuit" Series resistances add: 1,000 + 2,200 = 3,200 ohms. About688 is their parallel equivalent;1,200 is their difference;2,200 ignores the first resistor.

    Reference: DOE Fundamentals Handbook: Electrical Science, Volume 1 — Module 2, p. 23, Series Resistance