Abstract: A crime prevention apparatus for controlling the operation of an elevator which comprises a night detector for detecting night, a passenger detector for detecting the presence of only one adult passenger in an elevator cage and a start instructing unit for enabling the operation of the cage only when the passenger and the night detectors are operated, thereby allowing the operation of the cage only when one adult passenger rides in the cage during the night and thereby preventing most crimes from occuring in the cage during the night.

Abstract: A high power sonar pulse generator driven by a low power electrical motor erein a flywheel, placed in the mechanical system, connects the small motor and large generator. Since the large power output from the pulse generator is required only intermittently, the energy stored in the rotating flywheel allows a small motor to effectively drive the large output pulse generator while a braking effect on the flywheel is used to vary the sonar impulse producing an advantageous FM glide.

Abstract: A system for transmitting a parametrically pumped sonic signal through a transmission medium to a remote location is disclosed. The preferred system, which is particularly intended for use as a sonic weapon, comprises a sound source; means for separating the sound into a plurality of discrete frequency components including a fundamental component and at least one additional component, each additional component having a frequency twice that of the next lowest frequency component; means for adjusting the phase difference between each frequency component and the next lowest frequency component to substantially 90.degree.; means for colinearly focusing the components on the remote location; and means for rendering the transmission medium nonlinear between the focusing means and the remote location.

Abstract: A selected increase in the farfield amplitude of the difference frequency am of saturation limited parametric sonar sources is obtained by an array of saturation limited parametric sources having a center-to-center spacing selected such that the primary beams launched by each source coexist in a common region where attenuation has reduced the amplitude of each primary beam to a level which precludes saturation. The selected center-to-center spacing depends upon the number of individual sources implemented and each doubling of the number of selectively spaced sources provides at least a 3 dB increase in the farfield difference frequency amplitude without changing the nominal directivity characteristics of the parametric source.

Abstract: An echo sounder including a unit for transmitting, into a medium, acoustic signals at two slightly differing high frequencies and in the form of pulses, resulting in the creation of an acoustic signal in the medium at a low frequency equal to the difference between the two high frequencies, and a receiving unit including a receiving transducer for receiving echoes of acoustic signals at the difference frequency and a display device for recording the echo signals in accordance with their travel times, the display device having a signal input which is connected with the low frequency receiving transducer, is further provided with a second receiving transducer responsive to high signal frequencies for receiving echoes of acoustic signals at at least one of the two transmitting frequencies, and a member connecting the second receiving transducer to the signal input of the display device.

Abstract: Parametric array Doppler sonar apparatus includes an acoustic lens containing a flat disk-like central portion and an annular outer portion serving as a convergent lens. Multiple transducers are positioned between the lens and the focal plane so as to launch collimated acoustic beams in specified directions through the central portion of the lens and to receive reflected energy propagating principally through the annular portion of the lens.

Abstract: The invention relates to a device for measuring aquatic currents, placed on a moving boat comprising a Doppler effect sonar. The device comprises two sets of transducers and transmitting and receiving in the directions D.sub.1, D.sub.2, D.sub.3 and D.sub.4 forming an angle .+-..alpha. with the vertical z. A transmission circuit supplies impulses simultaneously at two frequencies f.sub.1 and f.sub.2. The receiving circuit processes the signals of the volume reverberation echos affected by the Doppler effect, corresponding to the frequencies f.sub.1 and f.sub.2, and the sea bed echo affected by the Doppler effect at the frequency F=f.sub.1 -f.sub.2, this frequency being generated by the non-linearity of the medium. Finally are obtained the profile of the horizontal velocities of the currents function of the depth.

Abstract: A beam of sound, of sufficient amplitude for inducing a finite amplitude effect in water, is directed into a field of sound for interaction therewith to produce intermodulation products. Energy is removed from the sound field in the formation of the intermodulation products resulting in an attenuation of sound in the sound field.

Abstract: This sonar system, placed on a vehicle such as a ship or a submarine, comprises transducer means for transmitting and receiving acoustic waves at two different frequencies, said reception means being adapted to generate echograms of the submerged surface from the received echoes of the transmitted pulses, the directivity diagram of said transducer means comprising a main transmission lobe whose axis is inclined with respect to a vertical line in a plane orthogonal to a first direction of displacement of the vehicle and a second transmission lobe oriented along a vertical line, means for determining the displacement velocity of the ship along said first direction, means for determining the water depth below the vehicle from the measured values of the propagation time of the waves transmitted along the direction of the secondary lobe and means for determining the displacement velocity of the vehicle in a direction orthogonal to the first one, by measuring the frequency of the acoustic waves received along a par

Abstract: A system for the determination of the direction of a source of sound in water utilizing the finite amplitude effect. A narrow beam of sonic energy at a frequency higher than that of the source is projected in a direction opposite the direction of the source. A hydrophone receiving beam intercepts the projector beam at a distance from the projector thereof, the distance being sufficient to permit a finite amplitude non-linear interaction of the projector beam energy and the energy of the source via a virtual end-fire array. Cross-modulation products resulting from the non-linear interaction are received by the hydrophone, the precision of measurement being dependent on the directivity pattern of the virtual end-fire array.

Abstract: An underwater mapping system in which a swath of terrain, much wider than a sonar beam width, is observed by means of a sonar beam scanned in the cross track plane of a ship. Filtering and correlation techniques are employed to compensate for distortions in echoes emanating from the ocean bottom by a selection of filter coefficients in accordance with the orientation of the sonar beams and by providing a simulated echo envelope for correlation.

Abstract: Digital beamsteering for a parametric scanning sonar steers a nonlinear, ulated signal of a single high frequency by appropriately delaying and/or varying the phase of the signal as it enters each of a plurality of elements in an array. The sonar beam can be steered electronically over a wide range of angles.