1. IN COMBINATION, A ROTARY SHAFT MOUNTED FOR ROTATION IN A NORMAL DIRECTION AND FOR ROTATION IN A REVERSE DIRECTION, MEANS LIMITING THE DEGREE OF ROTATION OF SAID SHAFT IN EITHER DIRECTION, A NORMALLY OPEN SWITCH HAVING A SWITCH OPERATING MEMBER AND AN ACTUATING ARM THEREFOR; SAID ACTUATING ARM HAVING AN ENLARGEMENT AT ONE END THEREOF; A CAM DICS MOUNTED ON SAID ROTARY OF THE LATTER BEING UNATTACHED TO SAID SHAFT FOR ROTATION OF THE LATTER INDEPENDENTLY RELATIVE THERETO; SAID CAM DISC HAVING A PERIPHERAL RECESS THEREIN FOR RECEIVING SAID ENLARGEMENT ON SAID SWITCH OPERATING ARM WHEN SAID SWITCH IS IN NORMAL OPEN POSITION; AND MEANS MOUNTED ON SAID SHAFT ADJACENT SAID CAM DISC FOR ROTATION OF SAID MEANS IN EITHER DIRECTION WITH SAID SHAFT; FURTHER MEANS ON SAID