A signal processor is described for object detection systems such as radar and sonar systems in which wave energy is transmitted and received as a train of discrete pulses of frequencies stepped in predetermined sequence. The received signal processor comprises a plurality of processing channels of number corresponding to the number of sub-pulses in the transmitted pulse train, each channel including frequency selective means such that signal returns of frequencies corresponding to but one of the transmitted sub-pulses are processed by that channel. Means are provided for simultaneously sampling the signal levels in all channels and indicating that channel in which the signal level is greatest, this sampling process being serially repeated at times related to each of the times of transmission of one sub-pulse of the train. The time sequence thus generated of the greatest amplitude signals in the several processor channels is compared or tallied against the sequence in which the sub-pulses of corresponding frequencies were originally transmitted, the occurrence of a match being taken as indicating a target at the range for which the sampling times were set.