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AND gate output condition

Aviation Mechanic General (AMG) practice question 11 of 41 on Fundamentals of Electricity and Electronics. ACS element AM.I.A.K22 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONWhen is the output of an AND gate high?

  1. AOnly when all of its inputs are high
  2. BWhen any one of its inputs is high
  3. COnly when all of its inputs are low, as in a NOR gate
Show the answer and explanation

Correct answer: A. Only when all of its inputs are high

  • A — correct The handbook states the output of an AND gate is high only when all of the inputs are high; if any input is low, the output is low.
  • B — incorrect An output that goes high when any input is high describes an OR gate, not an AND gate.
  • C — incorrect A high output only when all inputs are low is the behavior of a NOR gate; the AND gate produces a low output in that case.

BACKGROUND

Boolean logic represents truth values with the binary digits 1 and 0, and its fundamental operators are AND, OR, and NOT. An AND gate has two or more inputs and a single output; the output is high only when all of the inputs are high, and if any input is low the output is low. Its purpose is to determine when several conditions have been met at the same time, such as autopilot engage logic that requires the vertical gyro, directional gyro, control knobs, and servo circuits all to be valid. The inverter, or NOT gate, converts one logic state to the opposite, and a NOR gate is an OR function with an inverted output whose output is high only when all inputs are low.

STUDY TIP

Picture the handbook's two switches in series feeding a light bulb: both must be closed for the light to come on, which is AND logic.

KEY POINTS

  • AND gate: output high only when all inputs are high.
  • Any low input makes an AND gate output low.
  • OR goes high with any high input; NOR goes high only when all inputs are low.

SOURCES

  • FAA-H-8083-30B ch12 "Basic Logic Circuits" > "The AND Gate"
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SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-30B Aviation Maintenance Technician Handbook – General, 14 CFR part 43 and part 65. Regulations and handbooks are revised; confirm details against the current edition.