Abstract: A D/A conversion circuit has each branch of its resistive binary scaling network energized by a switchable network. Each switchable network employs the internal current paths of an Integrated Circuit (I.C.) solid state device, such as a Complementary-Metal-Oxide Semiconductor-Field-Effect-Transistor (CMOSFET) device, which provides complementary switching action. Each switchable network also employs a Metal-Silicon (M-S) diode, which provides clamping and diode switching actions. By a combination of I.C. device and M-S diode device actions, the following features are achieved in a single circuit: (A) high accuracies, (B) fast setting times and (C) low power consumption. Also disclosed is a cooperating variable D/A reference potential source which achieves temperature compensation.

Abstract: A programmable analog transversal filter is disclosed for processing analog signals and comprising a charge-coupled device (CCD) for receiving a series of discrete analog signals to be delayed by increasing periods and applied to the outputs of the CCD, and a plurality of MNOS memory devices coupled to the taps of the CCD and being programmed so that the output of a CCD tap is multiplied by a particlar factor. In particular, the MNOS memory devices are disposed in a matrix of rows and columns. The outputs of the MNOS memory devices of each row are summed and the row output signal e(t- ##EQU1## WHERE W.sub.k is the weighting factor associated with the K.sup.th MNOS memory device are applied to corresponding inputs of a parallel-to-series converter taking the form of a CCD. The parallel-to-series converter then is enabled to serially read out the row outputs. The weighting factors are set into the system by varying the threshold voltage of the corresponding MNOS device.

Abstract: Two pairs of acoustic transducers are provided for obtaining fluid current velocity measurements. The pairs of transducers are mounted in a supporting ring which introduces a controlled source of error in the measurement process, the configuration however resulting in a nearly constant error regardless of flow direction. The constant error introduced by the ring supporting structure may be easily corrected by a scaling factor in the signal processing circuitry utilized to compute fluid velocity.

Abstract: A method and means for controlling the output characteristics of a laser in which the optical axis of the laser output, either within the optical cavity of said laser or outside of said cavity, is transected with a fluid stream. The laser output may either be transected with a fluidic jet such as a jet of gas to modulate the output characteristics or the laser beam positioned by means of a directed flow of liquid across the optical axis thereof.

Abstract: Breathing gas from a remote source is supplied directly to a diver's helmet, without the requirement of a demand valve. Exhaust gas is returned back to the remote source through a series arrangement of a normally open fail-safe valve and an exhaust control valve which maintains the helmet pressure within predetermined limits relative to the ambient water pressure. Should the exhaust control valve fail in the open position, the fail-safe valve will actuate to insure that the helmet pressure does not decrease to a dangerous level. Valve actuation is a function of diver orientation so as to maintain helmet pressure within a range to minimize diver breathing effort, for the various positional orientations.

Abstract: Breathing gas from a remote source is supplied directly to a diver's helmet, without the requirement of a demand valve. Exhaust gas is returned back to the remote source through a series arrangement of a normally open fail-safe valve and an exhaust control valve which maintains the helmet pressure within predetermined limits relative to the ambient water pressure. Should the exhaust control valve fail in the open position, the fail-safe valve will actuate to insure that the helmet pressure does not decrease to a dangerous level. Valve actuation is a function of diver orientation so as to maintain helmet pressure within a range to minimize diver breathing effort, for the various positional orientations.The helmet includes ducting for the exhaust gas and the valves are constructed and arranged to sense the helmet pressure directly for comparison with the ambient water pressure acting on the respective valves.

Abstract: A large depth-of-field arc-transducer for use in sonar systems is provided in which at least one transducer element is positioned to lie along the arc of a circle of radius R. The active faces of the transducer elements are directed to a point that lies on a line normal to the plane of the arc and passes through the center thereof. The radius R is equal to between 0.3 to 0.6 Rs and, preferably about 0.5 Rs, where Rs is the distance from said point to the midpoint of the arc-transducer.An improved depth-of-field sonar system is provided where at least two arc-transducers are used having different radii, and preferably, where each radius R is equal to between 0.3 to 0.6 Rs.

Abstract: An analog-to-digital conversion circuit of the type employing a feedback-type, successive subranging mode of operation is provided. The circuit achieves bipolar input capability using an internal subranging A/C converter which has only a unipolar capability using a single level, unipolar, add-only binary summer to combine successive subranges. The foregoing have been achieved by means of a novel combination of relatively simple circuit elements which have fast settling times.

Abstract: An electromagnetic transmitting or receiving communications system with multiple polarization capability. In the transmit mode an input signal is divided between two signal processing channels which feed a dual mode radiation element for exciting orthogonal polarizations. The signals in the two channels are shifted in phase relative to one another prior to power amplification. In the receive mode first and second channels connected to the dual mode element process received signals of certain polarizations governed by phase shifting the channel signals relative to one another, the phase shifting taking place after amplification. Various parallel channels may be incorporated in the receive mode of operation to simultaneous process signals of the same, or other polarizations and when incorporated within an array having electronic beam steering, the polarization selection may at each respective channel be combined with the beam steering function.

Abstract: A high resolution side-looking sonar system wherein the focus is electronically varied with range such that any and all returns are in focus. Focusing is accomplished by time varying phase cancellation, the apparatus additionally forming multiple receiver beams for increasing search rate.

Abstract: A side looking sonar transducer which has sound absorbing material extending forwardly of the active surface of the transducer elements to diminish the acoustic response over a predetermined zone for reducing the effect of erroneous reflection signals.

Abstract: A plurality of transducers are positioned in the walls of a pipe conveying a fluid, the volumetric flow rate of which is to be measured. Opposed upstream and downstream transducers project acoustic energy toward one another through the fluid, along a plurality of parallel paths. Electronic circuitry coupled to the transducers provides an indication of the fluid velocity component along these paths and the values are modified by predetermined weighting factors. The transducers are placed in the pipe such that the acoustic paths are positioned at certain distances with respect to a reference.

Abstract: A method and means are disclosed for obtaining high pulse rate metal vapor laser transitions by vaporizing a metal halide of the desired metal. The vapor of the metal halide is transversely passed at at least sonic velocities through a discharge region where it is dissociated to provide a neutral metal atom excited to an upper laser level by electrons of sufficient energy to create resonance radiation trapping and a population inversion of the upper laser level. The flow rate is maintained to permit the excited metal atom to emit laser radiation by stimulated emission to a lower laser level in the discharge region and to remove the lower laser level atoms therefrom. Dissociation and excitation of the flowing metal atoms are repeated periodically.

Abstract: An improved antenna of a coaxial type utilizing Z-shaped slots disposed in the outer conductor to provide an omnidirectional antenna pattern. Current coupling to the slots is achieved by means of the transverse portion of the Z slot. Detuning effects due to the presence of a transmission line are compensated for by dielectrically loading the slots with a dielectric cover over the coaxial line and/or by lengthening the longitudinal arms of the Z. The longitudinal spacing between each slot and the length of the transverse portion of each slot are chosen while considering all line effects to obtain the required phase and amplitude relationships. The antenna consequently requires no additional coupling, tuning or phasing devices mounted within or without the coaxial line.

Abstract: Underwater breathing apparatus including a diver worn back pack having a hard outer shell and a soft flexible undersurface to conform to the diver's back. Breathing bags positioned between the undersurface and outer shell are connected to the undersurface so as to extend down the diver's back and be coextensive with his lungs. Gas circuit components are mounted on the inside of the shell. The apparatus makes contact with the diver's back, at a small area on the upper portion of his back, and, at the lower portion of the diver's back two extending projections from the shell receive a transverse strap which contacts the diver in the vicinity of the small of his back.

Abstract: The invention is directed to a method for obtaining pulsed metal vapor laser transitions. The method comprises placing a metal halide of the desired metal within an enclosure and vaporizing the metal halide to provide a metal halide vapor. The metal halide vapor is thereafter dissociated to provide ground state metal atoms of sufficient number density to create a condition for resonance trapping and, substantially simultaneously therewith, ground state metal atoms are excited to an upper laser level, while maintaining a sufficient number in the ground state to preserve said resonance radiation trapping condition, with electrons sufficiently energized to create a population inversion between the upper and lower laser level. The excited metal atom is permitted to emit laser radiation by stimulated emission to a lower laser level and the emission is resonated, preferably between a pair of externally mounted mirrors.

Abstract: An underwater floodlit scene is viewed by a TV camera. The first few active TV lines in the scan format, indicative of the illuminated field where backscatter is a minimum, are stored on a video disk. As the apparatus travels over a target area to be viewed, subsequent portions of the TV video signal from the minimum backscatter area are subsequently stored on the disk. The stored signals are then displayed on a TV monitor as a moving window display. The number of active TV lines gated for storage on the disk may be made proportional to the carrier vehicle speed, altitude and camera viewing angle, or field of view.

Abstract: An electro-optical system is disclosed for measuring rotational angle. The system includes a radiation source and reference linear polarizer in combination with a plurality of linear target polarizers. Photosensors are arranged to receive modulated light separately from an adjacent pair of target polarizers. Pulsed electrical output signals representative of the modulated light received by the photosensors are generated. Means are provided for comparing output signals from the sensors and generating a signal representative of rotational angle between the reference and target. The angle of rotation between the reference linear polarizer and the target linear polarizers is thereby converted to a representative signal which may be used to drive a servo motor or other device operatively connected to a rotatable element directly or indirectly. The reference polarizer may be held in a fixed position or it may be mounted on an independently rotatable element.