clock pulses c until stopped by signals coupled thereto from respective ones of the correlators 42 the stopping of the count signifying the times of arrival of the signals at the respective transducers 36 the counts of the counter 44 are coupled via line 66 to the beam steering unit 58 which senses the differences between the counts of the counters 44 these differences representing the relative delays between the times of incidence of the signal 28 upon respective ones of the transducers 36 since the differences in times of arrival of the signal 28 to the transducers 36 is a measure of the direction of a wavefront of the signal 28 relative to the array 34 the beam steering unit 58 in response to the counts on line 66 provides a digital number on line 68 which represents the direction of the wavefront of the signal 28 relative to the array 34 the blocks in the figure representing the transducers 36 are understood to include preamplifiers and filters as are customarily applied in sonar systems similarly the blocks representing the transducers 40 are understood to include power amplifiers and filters as are customarily utilized for generating a beam of sound the amplifiers providing sufficient intensity for the sound beam 32 to provide a finite amplitude effect in the water 70 of the ocean surrounding the submarine 20 for the desired finite amplitude effect to.