Abstract: A portable low frequency underwater acoustic projector having two circular diaphragms separated by a spacer ring with a pair of coils and oscillating masses being located in pipes connected to central opening in two diaphragms, the coils driving these masses in opposite directions. Central openings in each diaphragm have an associated pipe extending outward from the interior of the projector, the pipe having closed outer ends. The interior of the projector being gas filled to provide pressure compensation.

Abstract: A high security data storage and retrieval system is disclosed which includes a novel low-cost laser-etched data card which can be read from and written to using a capacitively-coupled interface. The card includes a plurality of first and second electrodes arranged in a checkerboard pattern on a non-conductive substrate. A plurality of conductive links are interconnected between adjacent first and second electrodes of the card. The checkerboard pattern of electrodes on the cards permits each first electrode to be connected to as many as three or more second electrodes. An interface module is provided which can selectively address each first electrode and any adjacent second electrode. By this arrangement, the subject system is capable of storing a greater amount of information on a card. This increase in stored information is useable to provide a high level of protection against counterfeit card production.

Abstract: A general purpose potentiostatic test system, used to provide potentiostatic control of test electrodes using a multiplexer in both the anodic and cathodic regimes. A built-in data switching and measurement subsystem enables rapid and precise determination of the set potentials as well as the test electrode currents. All the test electrodes can be placed in the same test tank and use a single auxiliary electrode.

Abstract: A Long Term Current Demand Control System which can be used in corrosion research is disclosed. The system is used to potentiostatically control several cathodes at several different set potentials. All cathodes can be placed in the same test tank and draw current from a single anode.

Abstract: An apparatus for automatically determining various stresses measured by a rectangular strain gage rosette. The apparatus receives signals from the rosette and provides signals representative of the maximum principal stress, the minimum principal stress and the maximum shear stress, the peak maximum principal stress, the minimum principal stress at the instant when the maximum principal stress is peaking, and the peak value of the shear stress. A first analog signal processor provides stress signals representative of the maximum principal stress, minimum principal stress and maximum shear stress for each instantaneous input signal amplitude from each arm of the strain gauge rosette, and a second signal processor receives the stress signals and provides output signals representative of the peak maximum principal stress, minimum principal stress at the instant of peak maximum principal stress, and peak maximum shear stress.

Abstract: A system for monitoring the integrity of a cable, for example a cable for towing a variable depth sonar body through the ocean, is described. Such a cable comprises a core of electrical wires surrounded by load bearing wires which are secured to the sonar body through a terminator. For various reasons cracks can appear in the load bearing wires and in extreme cases one or more of the wires may break. The monitoring system includes a transducer located near the terminator where the wires are most likely to crack or break and acoustic emissions caused by the incidence of cracks or breaks are picked up by the transducer. The resulting electrical signals are amplified and passed up the electrical core of the cable to the towing vessel where they are processed. Novel aspects of the system are the water coupling between the location of the cracks or breaks and the transducer and special processing circuitry which enables breaks, cracks and electrical noise to be distinguished from each other.