Abstract: A distance detecting apparatus has a transmitter for transmitting a cyclic output signal. The transmitter is digitally controlled to adjust the frequency of the output signal in relatively small increments through a band of frequencies. A receiver receives a cyclic reflected signal and has an adjustable center frequency of response. There is a device for adjusting the center frequency of response to correspond to the frequency of the output signal. The apparatus may have digital control for controlling the power level of the output signal. There may be a digital control for the gain of the receiver. The apparatus may also include a transducer for converting electrical signals to ultrasonic signals and include controls for adjusting the frequency of the output signal according to requirements of the transducer.