Definition
An electrical switch that controls three separate circuits simultaneously with a single operating action, opening or closing all three circuits at the same time. The switch has three independent sets of contacts (the three poles) that move together, and each set has only one position in which it makes contact (the single throw), meaning the switch is either fully on or fully off.
Plain English
One switch that turns three separate electrical circuits on or off at the same time. Flip it once and all three circuits change together. There is only an on position and an off position — no middle or alternate setting.
Context Anchor
Seen in aircraft electrical system descriptions, wiring diagrams, and maintenance troubleshooting.
Derivation
‘Pole’ refers to the number of separate circuits the switch can control — each pole is its own electrical path. ‘Throw’ refers to the number of positions where the switch makes contact. ‘Single-throw’ means only one closed position (plus an off position). So three-pole, single-throw literally describes a switch with three circuit paths, each with one on position.
Why Pilots Care
Pilots don’t typically operate these by part name, but understanding the pole/throw naming helps when reading wiring diagrams, troubleshooting electrical issues, or discussing systems with a mechanic.
Analogy
Think of one wall switch that turns three separate lights on and off together. There is one handle, but it controls three separate paths at the same time.
Intuition Check
“Three-pole” does not mean three separate switch handles. It means one switch handle controls three separate electrical paths.
Example Sentence 1
The cabin lighting system used a three-pole, single-throw switch so that the overhead, reading, and panel lights all came on together.
Example Sentence 2
Before starting the engine the pilot confirmed the three-pole single-throw switch was in the off position.