Abstract: A system applicable to acoustic, seismic, electromagnetic, hydrodynamic, and shock waves utilizing a map between signal time series and signal vectors defining the mathematical wave field model characterizing the signal's wave field. This map is developed from wave models relating field values to those on surfaces and corresponding uniqueness theorems. The system should allow for improved resolving power in bearing and elevation for discrimination of sources; detection and direction finding for signals below the average background level; detection based upon resolving power and signal vector characteristics rather than signal to noise ratio; reconstruction of signals of resolved sources for their transmitted information content; and multiple modes of operation. Adaptive incorporation of known undesired signals into the noise background and/or treatment of asymmetric background noise fields is permitted through use of a noise metric-based map yielding signal direction in the presence of diffraction effects.

Abstract: A system includes a receive line array that generates one or more receive line array signals, a processor operatively connected to the receive line array to process the receive line array signals and to generate detonation signals based upon the processed receive line array signal, and a modem operatively connected to the processor that transmits the detonation signals to one or more explosive line arrays, the explosive line arrays having at least one explosive charge coupled thereto that is detonated upon receipt of the detonation signals. The receive line array may include multiple sensors and multiple hydrophones. The sensors may be magnetic field, electric field, or electromagnetic sensors. The explosive line arrays may be detection line arrays or disruption line arrays. The modem may be configured to receive and transmit one or more user-initiated detonation signals to the disruption line arrays to detonate the disruption line arrays.

Abstract: A method and apparatus for determining the geophysical position of an autonomous underwater system utilizing underwater acoustic modems that exchange broadband underwater acoustic signals. The method of the invention includes the steps of initiating an exchange of broadband acoustic signals between the autonomous system of unknown geophysical position and a base system of known geophysical position wherein the depths of both systems is known. A bearing calculation is made on one of the signals transmitted between the systems, preferably through the use of an array of hydrophones placed closely together at predetermined locations on either the autonomous or base system. Also, the range between the two systems is determined by measuring the time of travel of at least one signal.

Abstract: Low-cost, reliable, easy to use device and method identifies potential drowning or near-drowning events (i.e. a submerged inert human) in a timely manner, provides the precise location of the event, and issues an alert that such an event is in progress. Device is optionally networked to remote monitoring station.

Abstract: A network of remote sensing node assemblies, a first and second of which each has a sensor element, as well as associated technique and program code for transmitting information collected about a liquid environment. The network provides the capability of sensing the liquid to collect a wide variety of types of information/data about the liquid and any surrounding environments, and transmitting from the originating node assembly to a different node within acoustic transmission range, and then transmitting further to a third node assembly where the information may be processed and communicated to a user, or further transmitted by way of suitable medium, preferably as electromagnetic signals, to a host location for processing into a compilation of data. Each of at least two sensing node assemblies has at least one sensor element adapted for operation while immersed within the liquid, a source of power, and a transducer for receiving acoustic waves/signals transmitted from another node assembly.

Abstract: An undersea communications system in which a message is converted to a redundant fixed-length data packet and transmitted acoustically as a quadrature phase-keyed signal in a frequency band with a continuous pilot signal at a frequency closely adjacent to the frequency band. A receiver uses the received continuous pilot signal to Doppler compensate the incoming quadrature phase keyed signal by estimating any Doppler distortion in the received pilot signal. The resultant redundant signals are then robustly processed coherently and jointly by the adaptive decision feedback equalizer and decoder to provide the original transmitted data.

Abstract: A system for the transmission of data by seismic wave, the system having at least one transmitting unit, that at least one transmitting unit comprising a first processing unit encoding a first signal, the first processing unit being coupled to a digital to analog converter, an amplifier amplifying the first signal, and a seismic pressure wave inducer transmitting the first signal to a geological feature; and at least one receiving unit, the receiving unit comprising at least one receiver coupled to the geological feature for receiving the first signal, and an analog to digital converter whereby the first signal is transferred from the geophone and is conveyed to a second processing unit, the second processing unit being configured to identify and decode the first signal.

Abstract: A system is provided for monitoring one or more depth associated parameters of an object submerged in water. A first set of alarm devices are mounted in the system's housing such that they are accessible from the exterior thereof. The first set of alarm devices, defined by an audio generator, a tactile generator, and a light, are initiated in accordance with a predetermined initiation scheme when at least one of the monitored parameters does not satisfy predetermined threshold criteria associated therewith. A second set of alarm devices are tethered to the system's housing for remote positioning with respect thereto. The second set of alarm devices utilize the same types of alarm devices as the first set of alarm devices and are also initiated in accordance with the predetermined initiation scheme.

Abstract: The present invention provides a system and method of use for recovering data from an area. The data are gathered with at least one sensor converting the data to a digital packet. The packet is processed as encoded data and the encoded data is stored as a data frame. A reader transmits a signal to a plurality of the sensors and replicates the signal. Each sensor produces a reflected signal in response to the transmit signal and assigns a modulation frequency to the reflected signal. The reader receives the reflected signal. The reader separates frequency components of the reflected signal into upper and lower sidebands and separates the sidebands into data channels. The reader outputs the encoded data by processing the data channels. The reader decodes the encoded data to retrieve the data packet and the environmental data.

Abstract: A platform with a sensor is for coupling to a submarine or other underwater vehicle and for sending data about the seascape to the submarine. In an embodiment, the platform is coupled to the submarine via a cable that has communication lines in it. The sensor may be attached to the platform via a mast. In an embodiment, the platform has a control surface, an anti-collision sensor, and a ballast. The platform allows a submarine to survey the seascape before rising to periscope depth.

Abstract: An underwater communications method and apparatus is provided for demodulating communications signals while compensating for the effects of range rate, i.e., relative velocity between the nodes of the communication system. The method of the invention is implemented in the DSP of an underwater bi-directional acoustic modem and method comprises the steps of generating a communication signal with an acquisition component for providing an initial estimate of the range rate. The acquisition component preferably is with a nonlinear frequency modulated acquisition component, preferably in the form of a hyperbolic frequency modulated signal, for providing the initial estimate of the range rate. Following this, a second set of signals, preferably a set of single frequency tonals, is generated and acquired using the initial estimate of range rate to obtain a more precise estimate of range rate.

Abstract: A system and method in which one or more acoustic projectors transmit broad bandwidth waveforms having known characteristics, and one or more acoustic receivers detect the transmitted waveforms, with the measurement of a propagation time from the projectors to the receivers being based on knowledge of the transmitted waveforms. The measurements are performed such that there is a low probability that other third party receivers will detect the transmission. The measurements may also be performed in an environment supporting multiple propagation paths. The system and method may further measure the Doppler shift induced by relative motion between the acoustic projector and the acoustic receiver.

Abstract: The present invention provides an acoustic transmitter for sequentially transmitting a plurality of pulse signals by sound. Each of the plurality of pulse signals is a signal of at least one modulated carrier wave, which has a predetermined frequency. The carrier wave of each of the pulse signals has a mutually different frequency. The transmitter performs amplitude modulation and/or phase modulation based on transmission information, and modulation by a signal indicating a window function, for the carrier wave of each of pulse signals. Then the transmitter sequentially transmits the plurality of pulse signals by sound.

Abstract: The present invention provides an attitude sensing device and method for determining an attitude of a reference axis of a package containing a fiber optic sensor sensor. The attitude sensing device comprises an electro-mechanical attitude sensor for generating an electrical signal indicative of the attitude sensor, and converter logic for converting the electrical signal into a stimulus signal. A local power source is preferably provided for the electro-mechanical attitude sensor in the converter logic. The stimulus signal is such that the fiber optical sensor is responsive to the stimulus signal to cause a variation in at least one predetermined property of an optical signal transmitted through the fiber optic sensor, the attitude of the reference axis being determinable from the variation of the predetermined property.

Abstract: For digital underwater transmission an information sequence (17) of digital bits is partitioned into a succession of symbols each comprising n bits where n is equal to or greater than one (2n potential symbols), each symbol (19) is replaced (20) a corresponding base code sequence of length m bits and the result (21) is passed to an acoustic transducer after bi-phase modulation (22) on a carrier. The code has good correlation properties, e.g. a pseudo-random maixmal length sequence, a Gold code or a Kasami code, and the value of m/n is at least (32). Preferably the base sequence is cyclically extended at one or both ends prior to modulation, and Solomon Reed redundancy coding (18) is initially applied to the information sequence. The output (23) of modulator (22) may be prefaced (26) by a pair of chirp waveforms (24). Provision is made for Doppler and multi-path correction.

Abstract: In a digital acoustic transmission device in which a digital sequence (31) is electrically modulated (22) on a carrier cos ?t, the modulated carrier (23) is prefaced with at least two pulse signals (24) of known timing relative to each other and to the modulated digital sequence to provide an output signal (13) for acoustic transmission. The pulse signals indicate to receiver the start of a transmission, and contain Doppler information for resampling the modulated signal prior to demodulation. Where the information sequence is in encoded blocks of equal length, the relationship between successive blocks can be used to update the Doppler information for use with the following block. Channel information can also be derived from the pulse signals and/or blocks for raking the next part of the incoming signal. Preferably the pulse signals have good correlation characteristics. In the embodiments the pulse signals are an immediately successive identical pair of linearly rising chirps.

Abstract: A wireless receiver for receiving an incoming signal having spatial and temporal diversity. The receiver uses noise-based prescaling of multiple receiver chain signals for optimally combining the receiver chain signals in a composite equalized signal and uses noise-based time-varying postscaling the equalized signal. The receiver determines noise-based scale factors by comparing signal symbols to dispersed replica symbols of a training sequence for the incoming signal.

Abstract: A wireless receiver for receiving an incoming signal having spatial and temporal diversity. The receiver uses noise-based prescaling of multiple receiver chain signals for optimally combining the receiver chain signals in a composite equalized signal and uses noise-based time-varying postscaling the equalized signal. The receiver determines noise-based scale factors by comparing signal symbols to dispersed replica symbols of a training sequence for the incoming signal.

Abstract: An apparatus for enabling acousto-optic communication comprising an in-water platform comprising means for emitting an acoustic signal to an acousto-optic interaction zone, an in-air platform comprising the ability for transmitting a first optical interrogation beam, the ability for receiving a portion of the first interrogation beam and a second laser beam formed from the reflection of the first interrogation beam off of the acousto-optic interaction zone, the ability for measuring and outputting a plurality of optical interferences between the portion of the first interrogation beam and the second reflected beam, and a signal converter receiving as input the plurality of optical interferences and outputting an electrical signal representing the received acoustic telemetry signal at the interrogation point at the air-water interface.

Abstract: In a first preferred embodiment, an underwater alert system (10) includes a transmitter assembly (12), carried by a first diver (14), that transmits a predetermined wireless signal (36) to a receiver assembly (16), carried by a mask (18) worn by a second diver (20), that generates an alert to gain the attention of the second diver (20). In a second preferred embodiment, the underwater alert system (10) includes a first transceiver assembly (232), carried by a mask worn by a first diver (14), communicating a predetermined wireless signal (36) with a second transceiver assembly (254), carried by a mask (18) worn by a second diver (20), to permit the first diver and second diver to gain each other's attention.

Abstract: The present invention provides a receiver for underwater acoustic telemetry which combines a decision feedback adaptive equalizer structure with a modified turbo-equalizer structure. The modified turbo-equalizer structure is of significantly reduced complexity because the decision feedback adaptive equalizer structure is operable to process a plurality of data channels to provide a single symbol data output stream for application to the input of the modified turbo-equalizer which uses a decision feedback equalized, interleaver, deinterleaver and a decoder. Either a hard viterbi decorder for single iteration processing or a soft in/soft out decorder such as a MAP decoder for multiple iteration can be used. The iteration provide improved performance compared to a normal DFE and lower complexity compared to the traditional turbo-equalizer.

Abstract: The present invention provides a receiver for underwater acoustic telemetry which combines a decision feedback adaptive equalizer structure with a turbo-equalizer structure. The turbo-equalizer structure is of significantly reduced complexity because the decision feedback adaptive equalizer structure is operable to pre-process a plurality of data channels to provide a single symbol data output stream for application to the input of the turbo-equalizer. The turbo-equalizer structure is also of reduced complexity due to use of a correlator to provide channel response data to the turbo-equalizer. The channel response data is produced by comparing received data comprising a training sequence with a locally produced training sequence.

Abstract: A buoy system bi-directionally communicates in-air and underwater. A buoy having a shell to float on water has an upper portion in air and a lower portion in water. An array of acoustic transducers which is disposed in the lower portion receives acoustic signals and transmits acoustic signals. A dome-shaped retro-reflective coating on the upper portion is vibrated for retro-reflecting impinging laser illumination as data signals in air. An array of photo-detectors on the upper portion are responsive to impinging laser control signals and/or signals which may be transmitted as acoustic signals in water.

Abstract: Dive computers and methods of logging information including position, audio and video information are disclosed. In one embodiment, the invention includes a processor, a global positioning system receiver connected to the processor and a pressure transducer connected to the processor.

Abstract: For digital underwater transmission an information sequence (17) of digital bits is partitioned into a succession of symbols each comprising n bits where n is equal to or greater than one (2n potential symbols), each symbol (19) is replaced (20) with a corresponding base code sequence of length m bits and the result (21) is passed to an acoustic transducer after bi-phase modulation (22) on a carrier. The code has good correlation properties, e.g. a pseudo-random maixmal length sequence, a Gold code or a Kasami code, and the value of m/n is at least (32). Preferably the base sequence is cyclically extended at one or both ends prior to modulation, and Solomon Reed redundancy coding (18) is initially applied to the information sequence. The output (23) of modulator (22) may be prefaced (26) by a pair of chirp waveforms (24). Provision is made for Doppler and multi-path correction.

Abstract: In a digital acoustic transmission device in which a digital information sequence (31) is electrically modulated (22) on a carrier cos &ohgr;t, the modulated carrier (23) is prefaced with at least two pulse signals (24) of known timing relative to each other and to the modulated digital sequence to provide an output signal (13) for acoustic transmission. The pulse signals indicate to receiver the start of a transmission, and contain Doppler information for resampling the modulated signal prior to demodulation. Where the information sequence is in encoded blocks of equal length, the relation between successive blocks can be used to update the Doppler information for use with a following block. Channel information can also be derived from the pulse signals and/or blocks for raking the next part of the incoming signal. Preferably the pulse signals have good correlation characteristics. In the embodiments the pulse signals are an immediately successive identical pair of linearly rising chirps.

Abstract: An untethered communications buoy system has an untethered buoy freely floating on the surface of water to not compromise the location of the submersible. The submersible has a cavity containing a first data interface member connected to a computer/data-storage that is connected to an acoustic transducer. The untethered buoy has a computer/memory module connected to a radio transceiver and acoustic transceiver. A second data interface member is connected to the computer/memory module and is mounted on the untethered buoy for fitting into the cavity and mating with the first data interface member. A ship is remotely located from the submersible and buoy and has a radio transceiver and an acoustic transceiver. Mating the first and second data interface members permits bidirectional downloading of data between the computer/data-storage and the computer/memory module.

Abstract: An underwater communication device in combination with a chemiluminescent glow stick. The combination comprises a rigid housing having a seat structure for receiving a chemiluminescent glow stick on an outer face of the housing and a loop structure on a second outer face of the housing for attachment to another object. A projectile resides within the rigid housing such that movement of the housing will cause the projectile to move within the housing impacting an inner surface of the housing causing sound vibrations. A chemiluminescent glow stick is engaged with the seat structure, illumination of the glow stick providing means for visual underwater communication. A means for maintaining engagement of the glow stick with the seat structure of the rigid housing maintains the glow stick against the seat structure.

Abstract: An apparatus for phase coherent underwater communications includes a transmitter; a receiver, including a processor for jointly performing coherent diversity combining, carrier recovery, channel equalization and synchronization; and an antenna array that includes a plurality of antenna sub-arrays for alternately transmitting a signal generated by the transmitter and for receiving an incoming signal. Each of the antenna sub-arrays includes a plurality of underwater sensors positioned such that each of the sensors is spaced at about one half the wavelength of the receiver/transmitter operating frequency from any adjacent sensor in the same sub-array. At least one of the sub-arrays has a centerpoint vertically spaced apart from a centerpoint of an adjacent sub-array at a distance about equal to or larger than a vertical correlation length of a received signal. The individual sub-arrays are beamformed, e.g. using a plane-wave delay-and-sum (or phase-steering) method.

Abstract: An apparatus for phase coherent underwater communications includes a transmitter; a receiver, including a processor for jointly performing coherent diversity combining, carrier recovery, channel equalization and synchronization; and an antenna array that includes a plurality of antenna sub-arrays for alternately transmitting a signal generated by the transmitter and for receiving an incoming signal. Each of the antenna sub-arrays includes a plurality of underwater sensors positioned such that each of the sensors is spaced at about one half the wavelength of the receiver/transmitter operating frequency from any adjacent sensor in the same sub-array. At least one of the sub-arrays has a centerpoint vertically spaced apart from a centerpoint of an adjacent sub-array at a distance about equal to or larger than a vertical correlation length of a received signal. The individual sub-arrays are beamformed, e.g. using a plane-wave delay-and-sum (or phase-steering) method.

Abstract: An underwater communication device in combination with a chemiluminescent glow stick. The combination comprises a rigid housing having a seat structure for receiving a chemiluminescent glow stick on an outer face of the housing and a loop structure on a second outer face of the housing for attachment to another object. A projectile resides within the rigid housing such that movement of the housing will cause the projectile to move within the housing impacting an inner surface of the housing causing sound vibrations. A chemiluminescent glow stick is engaged with the seat structure, illumination of the glow stick providing means for visual underwater communication. A means for maintaining engagement of the glow stick with the seat structure of the rigid housing maintains the glow stick against the seat structure.

Abstract: A system is disclosed that allows passage of electrical signals across a rigid boundary, such as a pressure hull of a submarine or vessel that operates in water. The passages provided by acoustic means are accomplished without any holes being made in the rigid boundary.

Abstract: A method for Doppler compensation in a phase coherent underwater communications system includes the steps of receiving a communications signal from a plurality of underwater communications channels, where the signal consists of a sequence of raw data; then applying a Doppler estimation to the data; demodulating the raw data; low pass filtering the demodulated raw data; applying resampling and downsampling to the data at a fractional sampling rate, for n samples per symbol, and generating a synchronized, Doppler-phase-corrected output signal; then applying the synchronized, Doppler-phase-corrected fractionally sampled signal to a phase locked loop and equalizer; then comparing an estimated symbol with a decision symbol and updating a plurality of tap coefficients; and h) outputting decision symbols.

Abstract: In a first preferred embodiment, an underwater alert system (10) comprises a transmitter assembly (12), a receiver assembly (16) and a mask (18). The transmitter assembly (12), carried by a first diver (14), has a waterproof transmitter housing (38) for carrying an alert switch (68), a transmitter (66) and a transmitting element (80). The alert switch (68) generates an electrical alert actuation signal (86) responsive to the alert switch (68) being actuated, either manually by the first diver (14) or automatically by the first diver's equipment. The transmitter (66) generates a predetermined electrical transmit signal (98) responsive to receiving the electrical alert actuation signal (86). The transmitting element (80) generates a predetermined wireless signal (36) responsive to receiving the predetermined electrical transmit signal (98).

Abstract: A device for acoustic communication of coded multi-channel digital messages in a liquid medium. The device is designed to use a single carrier frequency and includes the use of acoustic transducers in signal communication, and may include interfaces for communication with a variety of peripherals, host computing devices, and user communication and control devices. The device incorporates effective methods of encoding, transmitting, receiving, decoding, and acknowledgment of digital signals for achieving the desired level of reliability, bi-directional communication and multi-channel capability. The device is a communication subsystem configured to provide communication with another device of the present invention.

Abstract: A system is disclosed for locating swimmers who could be in danger of drowning, as determined by preset parameters such as the time duration that they remain at a depth where breathing is impossible. In this system, each individual swimmer wears a SONAR Swimmer Location Monitor (SSLM). This is a miniature electronic device that not only determines the extent of the swimmer's danger but also emits an ultrasonic alarm signal whenever such danger exists. At each occurrence, an alarm, which may be audible and/or visual, is sounded on the surface. Meanwhile the swimmer's location is tracked in real time from the signals received on a hydrophone array deployed along the perimeter of the swimming area. These signals are combined in a central processor and the computed real-time location is displayed graphically on a monitor to guide the guard personnel in rescue operations. The invention is intended for use in pools, beaches, water parks, and other swimming areas.

Abstract: A method and system are provided for communicating in a time-varying medium. A transmitter sends transmissions of the same message data separated in time with respect to one another. A single sensor receives the transmissions. Each received transmission is buffered until all of the transmissions that were sent are received. The buffered transmissions are simultaneously processed via multichannel adaptive equalization only when all of the transmissions that were sent are received.

Abstract: An underwater communication method, device, and system that enables bi-directional communication between and among under-water divers. In accordance with the present invention, messages may be transmitted and received between and among the divers in a network and/or between divers and a diving boat, buoy, or other reference point. The present invention also permits one or more divers to receive a homing signal and to move toward the source of that signal using an acquisition and tracking feature and functionality that utilizes a Doppler frequency shift and preferably a compass to determine the distance and direction of the source of the signal. The present invention also enables a diver in distress to broadcast a distress signal (i.e., SOS) that is received by every other diver within a predetermined distance from the distressed diver. The divers receiving the distress signal are then able to locate and rescue the distressed diver using the acquisition and tracking feature and functionality.

Abstract: An underwater intelligence gathering weapon system accurately places a weapon underwater and then communicates therewith from other platform(s). The weapon is equipped to maneuver through the air to a destination at the water's surface. A first transceiver, mounted onboard the weapon and coupled to the mine's logic portion, is activated after the weapon is in the water. The first transceiver can send and receive magneto-inductive signals. A second transceiver that sends and receives magneto-inductive signals is remotely located with respect to the first transceiver. Once deployed, the weapon can be controlled from a safe distance and can report any intelligence information collected by onboard sensors.

Abstract: A system for determining the sound velocity profile in a medium, such as water, includes an acoustic signal transmitting system at a transmitting location and an acoustic signal receiving and processing system at a receiving location. In one example, the acoustic signal receiving and processing system is located in a submarine or other similar vessel, and the acoustic signal transmitting system is located in an expendable vehicle or probe that moves throughout the water surrounding the submarine or vessel. At one or more transmission times and transmitting locations, the acoustic signal transmitting system transmits an acoustic signal. The acoustic signal receiving and processing system receives each acoustic signal at an arrival time and determines the sound velocity in the water between the transmitting location and the receiving location using the arrival time, the predetermined transmission time, and the predetermined transmitting location.

Abstract: A downhole communications system including an electromagnetic-to-acoustic signal repeater (35) for communicating information between surface equipment and downhole equipment and a method for use of the repeater (35) is disclosed. The repeater (35) comprises an electromagnetic receiver (37) and an acoustic transmitter (41). The receiver (37) receives an electromagnetic input signal and transforms the electromagnetic input signal to an electrical signal that is inputted into an electronics package (39) that amplifies the electrical signal and forwards the electrical signal to the transmitter (41) that transforms the electrical signal to an acoustic output signal that is acoustically transmitted.

Abstract: An underwater apparatus for transmitting and receiving high rate data and voice communication including a transmitter, a receiver, and a Doppler frequency shift compensator. The transmitter includes a data source comprising digital data to be transmitted by the apparatus through the water, a serial-to-parallel data processor for splitting the serial digital data into n parallel data channels, a n-channel modulator for receiving the n parallel data channels and for modulating those channels with n pairs of ultrasonic carriers to produce a modulated signal. The transmitter also includes a hydrophone for receiving and transmitting the modulated signal. The receiver includes a hydrophone for receiving a modulated signal.

Abstract: A system includes a first transducer and a second transducer coupled together through a coupling medium communicating undulating pressure wave from the first transducer to the second transducer for the transfer of electrical power from an external controller energizing the first transducer transducing the power signal into an undulating pressure wave communicated through the medium to the second transducer traducing the undulating pressure wave into an electrical response signal that can be converted into useful power for powering an embedded sensory and actuation control unit. The primary advantage of the system is the transfer of power through a coupling medium without the use of electrical power wires.

Abstract: A personal underwater communication device which comprises: A display; A memory unit for storing a plurality of preset messages, each message being assigned a common message identification code; Means for assigning a unique identification code to each personal device; Means for selecting one of said preset messages, to be transmitted to a receiving device; Means for selecting one or more receiving devices to which a message is to be transmitted; Means for producing a string encoding said message identification code and the identification code of the transmitting device; Means for modulating said string with at least one ultrasound acoustic modulating frequency, thereby to produce a modulated signal; Means for transmitting said modulated signal in water; Means in each device for receiving transmitted ultrasound acoustic modulated signals; Means for demodulating modulated signals which are received by said device, thereby to produce a demodulated string; Means for decoding a message from said demodulated string

Abstract: This invention relates to a secure marine communication system and especiy to a sonic communication system utilizing the so-called "sound channel" in the ocean deeps.The propagation of sound in sea water is known to occur along rays which are subject to refraction by variations in sound velocity. In most areas of the oceans, the velocity of sound varies with depth and temperature, and is less at some intermediate depth than it is either at the surface or at the ocean bottom. These oceanographic conditions produce a "sound channel" having at/its horizontal axis a level along which the velocity of sound reaches its minimum value. Essentially, the sound channel provides for a long-range transmission of sound between a sound source and a receiver where both types of sonic equipment are located at a level approximately corresponding to the axis of minimum velocity.

Abstract: A magneto-inductive submarine communication system and buoy provide two-way signal communications between a submerged craft, such as a submarine and remote command station that may be airborne, on the surface, or on land. A buoy released from the submarine and floating on the surface of the ocean and a satellite is included to complete the bidirectional communications. Messages and commands between the submerged craft and the buoy are communicated by magneto-inductive message signals and magneto-inductive command signals in the extremely low frequency (ELF) to very low frequency (VLF) range of less than 3000 Hz. Message and command communications between the buoy and the satellite (or aircraft, or helicopter, or surface ship), and the satellite to the station are transferred via radio frequency (RF) signals or laser emissions.

Abstract: An ultrasonic sound source broadcasts an ultrasonic signal which is amplitude and/or frequency modulated with an information input signal originating from an information input source. If the signals are amplitude modulated, a square root function of the information input signal is produced prior to modulation. The modulated signal, which may be amplified, is then broadcast via a projector unit, whereupon an individual or group of individuals located in the broadcast region detect the audible sound.

Abstract: A subsea repeater apparatus (48) for communicating information between surface equipment (60) and downhole equipment (44) is disclosed. The apparatus (48) comprises an electromagnetic receiver (66, 68) that receives an electromagnetic signal (46) carrying information from downhole equipment (44) and an acoustic modem (54) that acoustically retransmits (56) the information to surface equipment (60) through the sea. The apparatus (48) may also comprise an acoustic modem (54) that receives an acoustic signal (64) carrying information from surface equipment (60) through the sea and an electromagnetic transmitter (50) that radiates electromagnetic waves (66) carrying the information into the earth.

Abstract: A system includes a first transducer and a second transducer coupled together through a coupling medium communicating input and output undulating pressure waves between the first and second transducers for the transfer of input and output data between an external controller and an embedded sensory and actuating unit. The controller providing input data signals energizing the first transducer and the embedded unit providing output data signals energizing the second transducer collectively for bidirectional communication of data between the controller and embedded unit for functional sensor and actuator process control. The primary advantage of the system is the bidirectional transfer of data through a coupling medium without the use of electrical power wires for controlling embedded sensors and actuators.

Abstract: A seismic acoustic signal source includes a hull that has a wetted surface in contact with a body of water. When underway, the draft of the hull is substantially zero. An acoustic signal generator is provided with a linear actuator that is resiliently mounted in the hull. The linear actuator is acoustically coupled to the hull bottom such that when the signal generator is activated, the hull radiates an acoustic wavefield into the water.