Knife switch

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Knife switch

Open single-pole single-throw (SPST) knife switch
Electronic symbol

A knife switch is a type of switch used to control the flow of electricity in a circuit. It is composed of a hinge which allows a metal lever, or knife, to be lifted from or inserted into a slot or jaw. The hinge and jaw are both fixed to an insulated base, and the knife has an insulated handle. Current flows through the switch when the knife is pushed into the jaw. Knife switches can take several forms, including single-throw, in which the knife engages with only a single slot, and double-throw, in which the knife hinge is placed between two slots and can engage with either one. Multiple knives may be attached to a single handle and can be used to activate more than one circuit simultaneously; this is a multi-pole switch.