Apparatus for regulating the phase position of a controlled signal with respect to a reference signal comprising a source of the reference signal, a first delay means for delaying the reference signal by a given period of time, a second delay means for delaying the controlled signal for said given period of time, a first comparison means having a first input connected to said first delay means to receive the reference signal delayed by said given period of time and a second input to receive the controlled signal for generating a first binary signal whose value is an indication of the relative phases of the received signals, a second comparison means having a first input connected to said second delay means to receive the controlled signal delayed by said period of time and a second input to receive the reference signal for generating a second binary signal whose value is an indication of the relative phases of the received signals, combining means for combining the first and second binary signals to form a two-bit binary number, a controllable variable frequency oscillator means for generating the controlled signal, and control means connected to said combining means for controlling the frequency of said variable frequency oscillator means in accordance with the values of the first and second binary signals.