the nature of a single trigger or 34 start 34 pulse through ic1 as long as sw 1 remains closed only the single start pulse will be produced the recharge rate of c 8 is such that a second pulse will not usually be produced by the rear tires of the vehicle passing over the treadle 19 even if delayed passage of the vehicle produced a second pulse through ic1 it would merely reinstate the entire start sequence and allow even more time before the closing cycle begins in other words a subsequent start pulse whether produced by delayed passage of an initial vehicle or the subsequent passage of a second vehicle will merely restart the opening cycle providing additional time for safe passage a start pulse through ic1 makes the output at pin 5 of ic1 go low a hex inverter ic3 see lower right corner of fig4 commonly known as an ecg 4869 takes the low output pulse of ic1 and delivers a high output pulse to the master reset mr or pin 15 of the counter ic5 see upper left corner of fig5 this reset or 34 clear 34 pulse allows the master control counter ic5 to pass one series of control pulses from the oscillator ic6 a sequentially through the outputs o 0 o 8 inclusively as is evident in fig5 however only four of the control pulse outputs at o 0 o 5 o 6 and o 7 of ic5 are used in the present invention when the counter passes to o 9 the steady high output again disables the counter ic5 as it waits for another reset pulse each of the control pulses o 0 o 5 o 6 and o 7.