an automatic hand dryer contains a heating element and a motor which drives a squirrel cage fan . the fan exhausts air past the heating element to a downwardly - directed outlet . a base or mounting plate is adapted for flush mounting to a wall . the axis of the fan is peripendicular to the base plate and wall to which the dryer is attached . a control or sensing circuit emits signals to a detection zone beneath the outlet and monitors the zone for reflected signals indicative of a user &# 39 ; s presence . the circuit operates to energize and deenergize the power circuit to the fan motor and heating element . upon detection for a predetermined period , the circuit energizes the power circuit . the control circuit deenergizes the power circuit upon interruption of the reflected signals for a predetermined period , or after a predetermined maxium time period of continuous detection . under the latter condition , the stimulus reflecting the emitted signals must be removed from the detection zone to reactivate the control circuitry . any incremental interruption in the reflected signal which does not exceed the period of permitted interruption , restarts the commencement of the timing of the maximum period of continuous detection .