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Difficulty: EasySwitches and Relays

A technician needs to wire a single DC power source so that an operator can toggle power between an amber standby indicator and a green run indicator, ensuring only one light is energized at any given time. Which switch type should be selected?

  1. A
    Double-Pole, Single-Throw (DPST) switch
  2. Single-Pole, Double-Throw (SPDT) switchAnswer
  3. C
    Single-Pole, Single-Throw (SPST) switch
  4. D
    Inline thermal circuit breaker

Answer

Single-Pole, Double-Throw (SPDT) switch
A Single-Pole, Double-Throw (SPDT) switch features one common movable contact (the pole) that connects to either of two fixed output contacts (the throws). When flipped, it breaks contact with the first load and makes contact with the second, allowing selective operation between two indicators.

Step-by-Step Solution

1
Determine the number of input circuits (poles) required.
One input circuit (Single-Pole)
The circuit uses a single DC power feed connected to the switch's common terminal.
2
Determine the number of output positions (throws) required.
Two output paths (Double-Throw)
The operator must alternate power between two distinct loads (amber lamp and green lamp).
3
Combine the pole and throw specifications to identify the proper component.
SPDT switch
A single-pole, double-throw switch routes one common line to one of two selectable output terminals.

Key Concept

Switch Poles and Throws Nomenclature
Estimated Time:45s
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Topics

Switches and Relays

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