sensor will override the reference voltage on the operational amplifier 24 causing the output to rise to a positive state level which in turn will cause the bi stable multi vibrator 18 to change states the output of the bi stable multi vibrator 18 will place a low state signal on the inputs of transistors 25 and 26 thus causing the transistors 25 and 26 to cut off when transistor 26 cuts off its collector will begin to rise to a position level which is due to the charging action of capacitor 27 the time required for capacitor 27 to reach a positive enough level to trigger the operational amplifier 17 is determined by the rc time constant of capacitor 27 and resistor 38 the rc time constant has been set to be approximately one to two seconds which has been determined to be sufficient for the wipers to escape the parked position while capacitor 27 is charging the collector of transistor 25 is also rising to a high state level this change in the output level is felt on the input of both a field effect transistor fet 28 and a operational amplifier 30 the drain of fet 28 is connected across the normally closed contacts of a relay 29 if the operator of the vehicle decides to run the wipers in the high speed mode the relay 29 will energize disabling the control circuit from applying.