1. A COMBINATION INCLUDING A FIRST AND A SECOND ELECTROMAGNETIC CONTACTOR HAVING A FIRST AND SECOND OPERATING COIL, RESPECTIVELY; ELECTRICAL INTERLOCK MEANS FOR PREVENTING BOTH OF SAID COILS FROM BEING ENERGIZED AT THE SAME TIME; SAID INTERLOCK MEANS COMPRISING A FIRST AND A SECOND NORMALLY OPEN SWITCH; A THIRD AND A FOURTH NORMALLY CLOSED SWITCH; MEANS OPERATING SAID FIRST AND SAID THIRD SWITCHES TO CLOSED AND OPENED POSITIONS, RESPECTIVELY, WHEN SAID FIRST COIL IS ENERGIZED; MEANS OPERATING SAID SECOND AND FOURTH SWITCHES TO CLOSED AND OPEN POSITIONS, RESPECTIVELY, WHEN SAID SECOND COIL IS ENERGIZED; A FIRST ENERGIZING CIRCUIT FOR SAID COIL INCLUDING SAID FIRST COIL, SAID FIRST AND SAID FOURTH SWITCHES CONNECTED IN ELECTRICAL SERIES, WITH EACH OTHER; AND A SECOND ENERGIZING CIRCUIT FOR SAID SECOND COIL INCLUDING SAID SECOND COIL, SAID SECOND AND SAID THIRD SWITCHES CONNECTED IN ELECTRICAL SERIES WITH EACH OTHER.