Abstract: The switch unit, suitable for use in instances of emergency and also for a normal electrical shut-off and re-setting of a controlled system, features a snap-action electrical switch, as an example, a microswitch type control operated selectively (or jointly) by a pair of like end-anchored tension cables which have their inner ends connected to the unit's operating and re-set signal arm to trip the latter from a normal release position upon a tensioning of either cable by an attendant. The tripping of the arm causes it to operate the snap-action switch, and the arm is automatically locked in the tripped position thereof, having with said switch typically interrupted the electrical operation of the controlled system.