Abstract: In an echo-ranging homing torpedo having means for normally transmitting rch pulses at a predetermined repetition rate, and having a receiver wherein detection of target echo signals, during listening intervals between search pulse transmission instants, is limited by the presence of reverberation signals, said receiver including a TVG amplifier followed by a signal amplitude-threshold type of detection circuit for discrimination of target echo signals from said reverberation signals, the gain-increase characteristic of said TVG amplifier normally being set to limit target-echo detection sensitivity to an extent preventing false-alarm response under the maximum reverberation conditions which may occur during target search action, in combination:(a) means, responsive to initial detection of target echo signals, for switching said torpedo from a target search phase to a boresight homing phase of operation;(b) means becoming effective, when target echo detection occurs within an echo return time of preselected v