Allen-Bradley 800MS-H42B Selector Switch

Allen-Bradley 800MS-H42B is a two-position selector switch with a left-side spring-return and a contact set configured for 1 normally open (NO) and 1 normally closed (NC) circuit. In the active position the NO contact closes to complete a path while the NC contact opens, providing complementary outputs for simple control logic in industrial panels. The H42B designation identifies a specific operator/cam arrangement within the 800MS family, enabling consistent switching behavior across compatible components and standard wiring schemes. Typical applications include mode selection, control sequencing, and fail-safe interlock logic, where one path is energized while the other is de-energized, delivering clear, deterministic states in automation circuits.