Abstract: An automatic frequency control loop for maintaining a center carrier freqcy fed to a notch filter for blocking out system reverberation includes, along with the conventional elements found in an automatic frequency control loop, a control switching circuit responsive to excessive frequency deviations beyond a predetermined range as established in the AFC loop. Such excessive deviations are likely present during the time when little, if any, reverberation energy is received by a receiver carried on a moving platform, or, when signals originating from high energy level sources of countermeasure energy are being received. An interposed, selective device is included in the control switching circuit to permit operation in one of several modes as the situation demands. Including the control switching circuit in an active homing torpedo is the preferred application, although the teachings of the invention are applicable to all situations when own doppler nullification and reverberation damping is desired.