3. An underwater acoustic device comprising in combination an annular support member, a vacuum backed circular piezoelectric plate mounted on said support member, a substantially mechanically rigid wall element mounted on said support member and forming with the front face of said plate an enclosure, and an acoustic energy propagating liquid filling the free space within said enclosure, said liquid at all times being under a pressure no greater than atmospheric but not less than the vapor pressu...

1. A towable spread for surveying a water-submerged surface with a single towing vessel comprising at least two laterally spaced submarine vehicles of which at least one is dirigible, tow cables of substantially equal lengths attached to said vehicles, means operable under towing conditions to cause said vehicles to seek and maintain a preselected constant distance above the surface being surveyed, power means carried by the dirigible vehicle for steering the course of said dirigible vehicle, di...

1. In a sonic echo system for classifying objects proud on the ocean floor in which a submarine vehicle moves through the ocean at a constant height above the ocean floor, scanning means for simultaneously deriving separate electric signals corresponding to the sonic reflecting values of parallel strips of the ocean floor extending athwartships of said vehicle, means for simultaneously storing said separate signals on a record medium, and means for serially reproducing the stored signals.

1. A high resolution sound wave detecting system having a fan-shape beam of receiver sensitivity comprising a pair of transducers having elongated active faces coplanar and in end to end relation, an output signal channel for each transducer, means including two local oscillators of different frequencies connected to heterodyne against each other for producing timing pulses having a repetition rate equal to the frequency difference of said oscillators and individually against the output signals ...

1. Apparatus for destroying a ground mine lying proud on the ocean floor prising a self-propelled dirigible underwater vehicle carrying an explosive charge and having a catacoustic system for steering said vehicle in the azimuthal direction of a sound reflecting object, diving control surfaces carried by said vehicle, means for developing a control signal representative of the departure of the vehicle from a selected distance above the ocean floor, means responsive to said control signal for ope...

1. An apparatus for producing low frequency compressional waves under water hich comprises two circular plates spaced in opposed parallel relation, a plurality of reciprocating fluid motors arranged in parallel between said plates, an independent fluid pump hydraulically connected to each of said motors for driving the same, a by-pass valve for each motor adjustable to vary the length of the stroke of such motor, a prime mover coupled to drive all of the pumps in synchronism, whereby the motors ...

1. A towable detecting gear adapted for dragging over a water-submerged sace comprising a tail portion, a towing cable having its trailing end enclosed in a tail portion and having at least one insulated conductor, a weight member secured to said cable at the forward end of the tail portion and having sufficient negative buoyancy to drag along said submerged surface when under tow, a plurality of detecting devices disposed at intervals along the cable in said tail portion and in electrical commu...

1. In telemetric apparatus for sampling in rapid succession signal voltages f a given polarity on a plurality of information inputs, a signal voltage sampling network individual to each of said inputs and having first and second terminals, a semiconductor diode having its poles sharing said first and second terminals and arranged to conduct when a voltage of said given polarity is impressed on said second terminal, a single conductor serially connecting unlike poles of neighboring diodes for pro...