Question T6A08
From subelement T6 - T6A
What is the function of an SPDT switch?
Why is this correct?
An SPDT (Single Pole, Double Throw) switch has one input circuit (the pole) that can connect to either of two output circuits (the throws). Choice C correctly describes this function. Choice A describes an SPST (Single Pole, Single Throw) switch that simply turns one circuit on/off. Choices B and D incorrectly suggest the switch controls two separate input circuits, but 'single pole' means only one input circuit is controlled.
Memory tip
Remember the railroad analogy: SPDT is like a track switch with one input track that can route to either of two destination tracks. The key pattern is that 'poles' = inputs controlled, 'throws' = output positions available.
Learn more
SPDT switches are essential in amateur radio stations for antenna switching, band selection, and mode switching. They allow one signal source to route between two destinations without signal interruption. Understanding switch nomenclature helps when reading schematic diagrams and selecting appropriate switching components for station construction. The 'pole/throw' terminology appears throughout electrical engineering and helps identify switch capabilities at a glance.
Think about it
Why do you think amateur radio operators prefer SPDT switches over using two separate SPST switches when selecting between antennas?