Keyboard electro-mechanical switch with coil spring contact

A snap-action electro-mechanical switch comprising a resiliently stretchable electrically conductive ring-like switch contactor, guide means movably supporting said contactor, said guide means comprising a post having a step thereon extending transversely of the post, said guide means maintaining said contactor under contractile tension looped around said post and in sliding contact therewith, actuator means engaging said contactor and operable to press the same longitudinally of the post against said step, and said contactor being complementally formed whereby force exerted by said actuator pressing the contactor against said step effects abrupt expansion of the contactor permitting it to pass over said step with a snap action, a first switch contact means disposed adjacent to the post in position to be engaged by said contactor substantially as it passes over the step, and second switch contact means on the post in position to be engaged by the contactor with the contactor engaging the first contact means, whereby said snap action of the contactor is attended by substantially simultaneous stable electrical bridging contact between said contact means.