Abstract: A range measurement system for a submarine also having a passive monitoring system with a beam forming circuit, one beam of which may be selected by a signal V.sub.N from a tracking computer. Two assemblies of three hydrophones are located respectively on the port side and on the starboard side of the submarine. The signals supplied by these receivers are correlated with a beam signal S.sub.V of the passive monitoring system selected supplying the delays of these signals. A computer receiving these delay values supplies to the tracking computer the values of the bearing angle .alpha. and the distance D of the noise source.

Abstract: 1. A system for detecting in bearing a source of sound in a predetermined plane and for measuring the frequency of said sound comprising in combination: two hydrophone dipoles sustantially arranged in said plane, each having at least two hydrophones, the axis of said dipoles being at right angles to each other said hydrophones receiving said sound and providing output signals these hydrophones having respective axes perpendicular to said plane; means for detecting the respective phase shifts between said output signals of the same dipole and providing phase shift indicating signals; and display means having two inputs for receiving respectively said phase shift indicating signals.

Abstract: 1. A direction finding system for determining the direction from which short sonic or ultrasonic pulses are incoming, comprising: a plurality of electroacoustic transducers forming a circular arrangement; electronic means for sequentially switching in and out pairs of diametrically opposed transducers; differential means having two inputs, respectively connected by said electronic means to said switched-in transducers, and an output for providing the differential output signal of each of said pairs; and means for deriving the phase of said output signal.