Abstract: The automatic sweep and acquisition circuit for a phase locked loop includes a first circuit to detect when the error signal into the voltage controlled oscillator of an unlocked phase locked loop drifts to a DC voltage of a predetermined magnitude which represents an out-of-lock condition for the loop and this detected predetermined value is used to start the sweep waveform so as to regain a locked condition. Simultaneously with the start of the sweep waveform a dither tone is introduced into the loop filter which will not be fed back into the loop filter until the loop is locked. This fed back tone is detected and used to turn off or disconnect the sweep voltage and the dither tone.