Abstract: A phase lock loop operable with narrow band filtering characteristics in-lock and wideband acquisition characteristics when an out-of-lock condition is detected. The phase lock loop comprises a phase detector coupled to a differential amplifier to which a step ramp voltage is also coupled when an a.c. signal, which indicates an out-of-lock condition, is coupled from the phase detector to an out-of-lock detector. The a.c. signal from the phase detector also causes a switch means to short out a narrow band filter which is serially coupled with a wideband filter between the differential amplifier and a voltage controlled oscillator. The frequency of the voltage controlled oscillator is caused to vary by the a.c. signal until lock-in is achieved at which time, the out-of-lock detector stops and holds the step ramp voltage at the value required to achieve lock and the switch means reintroduces the narrow band filter to the loop.