1. IN A BRUSHLESS ZERO SPEED SWITCH; A STATIONARY BODY HAVING A HORIZONTAL BORE THEREIN, TERMINALS ARRANGED IN AXIALLY SPACED RELATION EXTENDING FROM OUTSIDE SAID BODY INTO SAID BORE AND INSULATINGLY SUPPORTED BY SAID BODY, A BODY OF MERCURY IN SAID BORE NORMALLY ELECTRICALLY INTERCONNECTING SAID TERMINALS, A ROTOR IN SAID BORE ROTATABLY SUPPORTED ON THE AXIS OF THE BORE, SAID BORE BEIN SEALED AT ITS OPPOSITE ENDS TO RETAIN THE MERCURY THEREIN, SAID ROTOR HVING AT LEAST A PORTION BETWEN SAID TERMINALS HAVING FLUTE MEANS SPIRALLING THEREALONG IN THE LONGITUDINAL DIRECTION WHEREBY THE ROTOR WILL ACT AS AN IMPELLER WHEN ROTATING AND PUMP THE MERCURY AXIALLY TOWARD ONE END OF THE BORE AND THEREBY INTERRUPT THE CONTINUITY OF THE BODY OF MERCURY TO BREAK THE CIRCUIT BETWEEN SAID TERMINALS, AND MEANS FOR ROTATING SAID ROTOR, SAID ROTOR AND SAID BORE BEING CONFIGURATED TO PRIVIDE RETURN PASSAGEWAYS FOR SAID MERCURY, WHEREBY WHEN SAID ROTOR IS ROTATED BELOW A PREDETERMINED SPEED SAID MERCURY FORMS A UNITARY BODY ESTABLISHING A CONDUCTIVE ELECTRICAL PATH BETWEEN SAID ELECTRODES.