1. IN COMBINATION A RUNWAY ALONG WHICH WORKPIECES ARE ADAPTED TO TRAVEL, A SWITCH ACUATING MECHANISM COMPRISING A SUPPORTING PLATE ATTACHED TO THE RUNWAY, AN ARM PIVOTED ON THE SUPPORTING PLATE, AT LEAST ONE OPERATING RAIL NORMALLY PROJECTING THROUGH AND ONLY SLIGHTLY ABOVE THE SURFACE OF THE RUNWAY ALONG WHICH WORKPIECES ARE ADAPTED TO TRAVEL SO AS TO NOT INTERFERE WITH THE TRAVEL OF WORKPIECES THEREOVER WHEN IN SAID RAISED POSITION, MEANS MOUNTED ON THE SUPPORTING PLATE INTERPOSED BETWEEN THE OPERATING RAIL AND THE ARM WHEREBY MOVEMENT OF EITHER THE RAIL OR THE ARM IMPARTS MOVEMENT TO THE OTHER, MEANS CONNECTED TO THE ARM FOR RETAINING THE OPERATING RAIL IN ITS RAISED POSITION UNTIL A PREDETERMINED PLURALITY OF WORKPIECES ACCUMULATES THEREON WHEREUPON SAID RAIL IS DEPRESSED INTO SUBSTANTIAL ALIGNMENT WITH THE RUNWAY, AND A SWITCH ACTUATING MEMBER ASSOCIATED WITH THE ARM FOR OPERATING A SWITCH MOUNTED IN FIXED RELATION TO THE SUPPORTING PLATE, SAID INTERPOSED MEANS INCLUDING MEANS WHEREBY THE UPPER SURFACE OF THE OPERATING RAIL IS MAINTAINED AT ALL TIMES PARALLEL THROUGHOUT THE MAJOR PORTION OF ITS LENGTH WITH SAID SURFACE OF THE RUNWAY.