Abstract: A dual frequency, synthetic aperture, sonar system includes a transmitter r projecting insonifying pings alternatively at first and second frequencies and a linear receiving array carried by a vehicle so as to receive returns from said pings. The first and second frequency returns are separated and subjected to processing in parallel channels where they are resolved into in-phase and quadrature components for subsequent phase-error correction, coherent addition, and synthetic aperture beamforming.

Abstract: A sonar system having a transmitting transducer adapted for being moved ag a predetermined path, a transmitter for energizing said transmitting transducer, an omni-directional receiving transducer spatially disposed behind said transmitting transducer, a sidewardly and downwardly looking receiving transducer contiguously disposed with said omni-directional receiving transducer, a receiver connected to the output of said sidewardly and downwardly looking transducer, a series connected detector, differentiator, delay, and time base generator coupled to the output of said omni-directional transducer, and a readout connected to the outputs of the aforesaid receiver and time base generator.

Abstract: An electronic barrier utilizes a bifurcated beam of wave energy to establ a barrier area having a null between the forks thereof. Objects encroaching on said beam cause a portion thereof to be scattered in the foreward direction. Suitable receiver equipment located remote from the source of the bifurcated beam and responsive to the foreward scattered beam is connected to provide an indication of said encroachment.

Abstract: A sonar system having a sonar transmitter which is programmed to broadcast wo sets of several increasing frequency signals, with the frequency gap between each set thereof sufficient to cause them to distinguish between deep and shallow water targets, respectively. A heterodyne receiver receives target echoes of said sets of several frequency signals and converts them to two sets of identical frequency signals which are then readout as a single continuous target display signal.

Abstract: A sonar system having a transmitter for successively broadcasting a pair of coustical signals having different frequencies, a programmer for determining the times said pair of signals are broadcast, a receiver for receiving said pair of signals after they have been reflected from a target, a programmer for effecting the conversion of said received pair of signals into a continuous unitary electrical signal having variable consecutive time periods which alternately contain the respective frequencies thereof, and a readout for displaying said continuous unitary electrical signal.

Abstract: A system for sweeping acoustic and magnetic mines or a combination of both s disclosed as comprising a pair of spatially disposed magnetic pipes that are held in their respective spatial dispositions by front and rear straps, and an acoustical energy generating pipe suspended between said front and rear straps by hinges in such manner that it is also disposed between said pair of spatially disposed magnetic pipes. A tractor vehicle moves all of the aforesaid pipes and their associated elements as a unit along a course intended to be cleared of acoustic and/or magnetic mines.

Abstract: The received signal from an acoustic echo detection and ranging system is mpared with internally generated signals indicating the focus of a variable focus transducer. Logic circuits in the signal comparison channel develop control voltages to focus said transducer upon a predetermined area from which said received signal originates.

Abstract: A magnetic compass is illuminated by a light emitting diode. The compass is nclosed in a case made of a lightweight, plastic composite material. The light-emitting diode is energized by a low profile, nonmagnetic battery connected to the light emitting diode through a nonmagnetic microswitch operated on the exterior of the casing by a pushbutton. The compass has a compass rose with strips of phosphorescent material disposed thereon, a rotatable bezel with a strip of phosphorescent material thereon and a lid having a sighting slot therein traversed by a cross hair. Located at the bottom and top of the cross hair are additional strips of phosphorescent material so that the compass may be utilized in the dark. The phosphorescent material may be charged by ambient light and by light emitted by the light emitting diode.