SPDT stands for?

• A. Single-pole, single-throw.
• B. Single-pole, double-throw.
• C. Single-throw, double-pole.
• D. Double-pole, double-throw.

Answer: (B)

SPDT stands for single-pole, double-throw. The “pole” is the one moving contact, and the “throws” are the two fixed contacts it can connect to. In one switch position the pole connects to one throw, and in the other position it connects to the other, allowing one input to be routed to either of two outputs. This is different from a single-pole, single-throw switch, which only has one path (on/off), and from a double-pole, double-throw switch, which has two independent poles each with two throws. So the best description is a single input that can be connected to one of two outputs.