three-way switch (US); two-way switch (UK)
Electrical switch that controls a light from two locations. In Japanese wiring terminology, 三路スイッチ corresponds to a three-way switch in US English and a two-way switch in UK English. Compare with 片切スイッチ (single-pole switch) and ４路スイッチ (four-way/intermediate switch).
See also: 片切スイッチ (かたぎりスイッチ) · ４路スイッチ (よんろスイッチ)
It's convenient to install three-way switches at the top and bottom of the stairs.
Standard kanji spelling using the numeral 三.
Variant using the Arabic numeral ３; common in technical contexts.
Compound of 三路 (さんろ, 'three-way') and スイッチ ('switch'), a technical term in electrical wiring.