Abstract: An underwater diving assistant device. In one embodiment, the present invention comprises a hand-held unit including a display screen. Messages and drawings are written on the display screen using a passive electromagnetic pen. Markings on the screen can be instantly cleared, stored or transmitted to another, similar device by placing the electromagnetic pen in proximity to a command icon on the screen. The unit includes standard dive computer functions. In one embodiment, the unit includes a digital camera and a vessel locator, and generates audible tones under various circumstances. In one embodiment, a power source of the unit is stored in a container fastened to a diver's weight belt and is connected by a tether to the unit.

Abstract: An oceanographic sampling system includes two or more underwater vehicles disposed in an array and an array controller for controlling the array of underwater vehicles as data is acquired. Each underwater vehicle includes a propulsion system for moving the underwater vehicle independently of the other underwater vehicles, a sensor for sensing an ocean parameter and providing sensor data representative of the ocean parameter as the underwater vehicle moves, a navigation subsystem for determining position data representative of the position of the underwater vehicle as the sensor data is acquired and a synchronizing subsystem for time synchronizing the sensor data and the position data acquired by the underwater vehicle with sensor data and position data acquired by other underwater vehicles. The array of underwater vehicles may function as a large aperture phased array, and phased array analysis techniques may be applied to the time-synchronized sensor data and position data.

Abstract: A submarine deployed sea-state sensor comprises an elongated housing having nose cone and an aft end, the housing having a forward buoyant chamber for receiving an accelerometer. Aft of the buoyant chamber, a damping assembly communication link deployment means and a lifting body are provided. Both the damping assembly and the lifting body are attached to a communication link interconnecting the accelerometer and a submerged platform so that, when the portion of the communication link between the lifting body and the submerged platform becomes taught, the lifting body is pulled from the housing. The damping assembly includes a motion damping body mounted on the buoyant chamber through an extendable telescoping arm. The extension of the arm is controlled by a pressure release spring, so that, when the sensor reaches a selected depth the telescoping arm will extend to project the motion damping body aftwardly.

Abstract: A communication and position determining device for use in an underwater communication and position determining system wherein the device transmits a sequence of one or more data words, wherein each data word includes a plurality of data bits transmitted in parallel as a corresponding number of concurrently transmitted signals, each of which occupies a different frequency band. The signals have waveforms selected from a pair of fade resistant waveforms that can be discriminated from one another, to represent binary data and the frequency bands are separated from one another by guard bands having widths sufficient to prevent intersymbol interference between the signals representing the data bits of a data word due, for example, to doppler and phase/frequency shifting, and successive data words are separated sequentially in time by intervals having a duration sufficient to prevent intersymbol interference between the signals of successive data words due to multipath reverberation.

Abstract: A towed array includes an array of N hydrophone groups and one or more nocoustic sensor modules structurally connected in-line with the array of hydrophone groups. The hydrophone groups and non-acoustic sensor module(s) are coupled to a common data transmission line. Each of the hydrophone groups defines a portion of an acoustic aperture occupying a specified length of the towed array. Each non-acoustic sensor module has a length that is n times the specified length where n is a whole number multiple of the total number of hydrophone groups.

Abstract: A self-propelled turbo siren modulator assembly is disclosed for use in an MWD system. The turbo siren includes a fixed turbine deflector located upstream from a rotor, which in turn is located upstream from a fixed stator. Drilling mud flowing through the turbine deflector causes the rotor to rotate independent of any external drive device. The rotor and stator preferably have a similar configuration, which includes at least one lobe and at least one port so that the rotor alternatively blocks or permits mud flow through the port(s) of the stator to create a cyclical acoustic wave signal, with a frequency that depends upon the number of lobes on the rotor and the velocity of the drilling mud. Encoded measurement data is modulated on the carrier frequency wave through the use of amplitude modulation, frequency modulation or phase shift modulation, or a combination thereof to maximize data rates.

Abstract: The present invention comprises a wide-band omni telemetry system adapted r increasing the signal transmission bandwidth of an existing tactical array having a single shared transmission line. In accordance with one embodiment of the invention electronic elements are provided for conditioning and converting a wide-band analog data signal, received from an underwater acoustic sensing device, to an appropriate wide-band digital signal. Timing elements provide a carrier wave signal interface with telemetry elements for modulating the carrier wave signal with the wide-band digital signal wherein the carrier wave is quadrature phase shift key modulated. In this way two separate carrier waves are created that are shifted in phase by about 90.degree. relative to one another.

Abstract: A signal shift compensation system and method compensates for a shift in a ignal, such as a Doppler shift in an acoustic signal. The system includes a signal sampler for oversampling the shifted signal at a fixed oversampling rate to establish an oversampled shifted signal digital value sequence. The fixed sampling rate is greater than the typical sampling rate, such as the Nyquist rate, of the signals by an oversampling factor. The system further includes a compensation downsampler for decimating the oversampled Doppler shifted signal according to a downsampling factor to establish a decimated digital value sequence. The downsampling factor is determined according to the oversampling factor by which the signal is oversampled and an estimate of the (Doppler) shift value. In one example, the downsampling factor is equal to the oversampling factor divided by a Doppler multiplier reflecting the Doppler shift.

Abstract: An underwater communication system by coded pulses, includes a transmitter placed at a surface of a body of water, for transmitting coded pulses, the transmitter having a transmitter circuit for generating the coded pulses, the transmitter circuit including a first shift register pre-programmed with a binary code corresponding to the coded pulses, and an underwater piezoelectric transducer for submersion in the water and electrically connected with the transmitter circuit for transmitting the coded pulses through the water; an underwater receiver for receiving the transmitted coded pulses, without any physical connection between the transmitter and receiver, the receiver having an underwater piezoelectric transducer, submerged in the water, for receiving the transmitted coded pulses, and a receiver circuit for comparing the received code pulses with stored coded pulses, the receiver circuit including an amplifier for amplifying the received coded pulses, an internal clock generator for generating a clock sign

Abstract: An adaptive oceanographic sampling system includes several stationary acoustic tomography units distributed in an ocean volume, a processing and control system and at least one underwater vehicle movable within the ocean volume. Each of the acoustic tomography units includes an acoustic source for transmitting acoustic energy in the ocean volume, a receiver array for generating acoustic tomography data in response to received acoustic energy and a transmitter for transmitting the acoustic tomography data. The acoustic tomography data represents an ocean characteristic in the ocean volume. The processing and control system analyzes the acoustic tomography data and determines a region of interest within the ocean volume. The processing and control system then directs the underwater vehicle to move to the region of interest. The underwater vehicle includes a sensor for sensing an ocean parameter and providing sensor data representative of the ocean parameter in the region of interest.

Abstract: Disclosed is a protocol for transmitting data in a towed hydrophone streamer, including a transmission method and a data frame. The method comprises the steps of (1) receiving a portion of the data frame into a data transmission circuit within a particular module of the streamer, the portion of the data frame representing telemetry data derived from an adjacent module, the transmission circuit transmitting the portion of the data frame to a desired destination, (2) receiving an end-of-data signal into the transmission circuit, the end-of-data signal commanding the transmission circuit to add telemetry data derived from the particular module to the portion of the data frame and (3) adding the data derived from the particular module to the portion of the data frame, the data frame thereby transmitted to the destination and including the data derived from the particular module, the telemetry data ordered within the frame as a function of an order of modules within the streamer.

Abstract: A preamplifier and pre-emphasis network is provided having a differential plifier exhibiting common mode noise rejection. The preamplifier is particularly suited for use with a double-sided sensor element and it includes a double-sided, balanced calibration circuit. First and second variable gain buffers are joined to the differential amplifier for preventing current noise degradation at the differential amplifier inputs. A pre-emphasis network is further provided in conjunction with the variable gain buffers for providing balanced differential gain of the sensor element signal. Further elements of the invention provide for high and low pass filtering, and differential buffering of the output signal.

Abstract: A bi-directional underwater communication system provides a submerged operator the ability to communicate with a surface operator. Provides two transceivers both containing keypads and displays capable of transmitting and receiving alpha-numeric data. The underwater transceiver is connected to a floating antenna assembly via a small cable.

Abstract: A method for underwater, acoustic transmission, characterized in that at the transmitting side, the signal to be transmitted first is sampled, digitized and stored and then un-sampled and un-digitized at a frequency less than the sampling frequency and is thus transmitted in analogue form, and in that at the receiving side the signal is correspondingly sampled, digitized and stored at the said un-sampling and un-digitizing frequency and then is re-read at the said sampling frequency.

Abstract: An underwater acoustic telemetry system uses spatially distributed receivers with aperture sizes from 0.35 to 20 m. Output from each receiver is assigned a quality measure based on the estimated error rate, and the data, weighted by the quality measure, is combined and decoded. The quality measure is derived from a Viterbi error-correction decoder operating on each receiver. The quality estimator exploits the signal and noise differential travel times to individual sensors. The spatial coherence structure of the shallow-water acoustic channel shows relatively low signal coherence at separations as short as 0.35 m. Increasing receiver spacing beyond 5 m offers additional benefits in the presence of impulsive noise and larger scale inhomogeneities in the acoustic field. Diversity combining, even with only two receivers, can lower uncoded error rates by up to several orders of magnitude while providing immunity to transducer jamming or failure.

Abstract: The present invention relates to a method and a transmitter/receiver for transferring signals through a medium in pipes or hoses, whereby at a transmitter side pressure pulses are generated of various frequencies or in various frequency ranges, and for the purpose of providing a technology which eliminates error sources, it is proposed according to the invention that the pressure pulses be generated at the transmitter side as an organised and defined bit pattern in order thereby to achieve one or two-way alphanumeric communication.

Abstract: An apparatus and improved method for transmitting an information signal. According to the improved method, an information signal is transmitted under water from a transmitter located at a first place to a receiver located distant therefrom at a second place. In performing the signal transmission, a modulated ultrasound carrier signal is delivered to the water and is formed with a fixed amplitude value in the transmitter. The modulation is performed by pulse duration modulating (with an information signal) the ultrasound carrier signal which, in turn, has a given frequency. The modulated ultrasound carrier signal is then picked up from the water and is demodulated in the receiver in order to recover the information signal.

Abstract: The invention relates to diver-to-diver communication apparatus. There is provided a communication apparatus (2) for diver to diver communication, the apparatus comprising a waterproof casing (4), power supply means (52), ultra acoustic transmission means (72), ultra acoustic reception means (72, 74), control means (56) for the ultra acoustic transmissions, monitoring means (56) for the ultra acoustic reception, and means (16) to actuate the transmission means (72); whereby upon actuation of the transmission means (72) a predetermined signal is transmitted by the transmission means (72) suitable for reception by the reception means (72, 74) of another diver using similar apparatus (2).

Abstract: The secure communication keying system has a noise generator whose output a predetermined finite band of noise within, for example, the zero to eleven hundred cycle per second range. The noise generator may be a pseudorandom noise generator that is synchronized with a given clock frequency. The output of the system may have noise-like characteristics, but it is encoded with any type of intelligence desired to be transmitted. The output signals simulate the ambient noise occurring within the communication medium and has the same frequency spectrum regardless of the frequency of the modulating signals supplied thereto.

Abstract: A transponder of an active digital sonar system identifies a multifrequency underwater activating sonar signal received from a remote sonar transmitter. The transponder includes a transducer that receives acoustic waves, including the activating sonar signal, and generates an analog electrical receipt signal. The analog electrical receipt signal is converted to a digital receipt signal and cross-correlated with a digital transmission signal pattern corresponding to the activating sonar signal. A relative peak in the cross-correlation value is indicative of the activating sonar signal having been received by the transponder. In response to identifying the activating sonar signal, the transponder transmits a responding multifrequency sonar signal.

Abstract: A remotely controlled radio telemetry buoy serves as a communication link tween an underwater acoustic interrogation/receiving transponder system and a remotely located surface platform. The buoy houses a transmission device, a transceiver device and a controller. The transmission device transmits data received from the transponder system as electromagnetic energy in a frequency range of 162-173 MHz. The transceiver device exchanges digital control signals between the surface platform and the buoy in the frequency range of 2-16 MHz. The controller transfers the control signals between the transceiver device and the transmission device and the transponder system.

Abstract: A multiuser receiver for use in additive white Gaussian noise, multiple-access communication channels. The receiver includes an interference estimator which estimates multiple-access interference signals using a variable weighting provided by a soft decision processor. The interference estimator may receive signals from matched-filter/sample-and-hold circuits, decorrelator circuits, or sliding-window-decorrelator circuits. The soft decision processor is provided having a soft-decision nonlinearity characteristic, which may correspond to a multilevel quantizer characteristic, a dead-zone nonlinearity characteristic, or a linear clipper characteristic.

Abstract: A hydroacoustic communication system employs spread spectrum to mitigate multipath interference caused by acoustic reflections off underwater surfaces and other large boundaries or acoustic discontinuities. The system is particularly beneficial for mitigating errors due to surface reflections, and for mitigating interference due to unwanted signals having a delay ranging from tens of microseconds to hundreds of milliseconds.

Abstract: Submarines are provided with underwater self-propelled vehicles that are nched from the submarines and guided by trailing fiber optic cables. Each underwater vehicle has a hull that is separable, and that defines a socket for mating with one end of the separable forward hull portion of another identical vehicle. The separable hull portions of one vehicle, when separated remain connected by a fiber optic line so that a homing device on this line can be used to link up with the transponder aboard the other vehicle. Wings on the latter vehicle guide the line toward a socket that accepts or mates with the end of the one vehicle hull portion.

Abstract: The positions of one or more underwater divers or vehicles are determined through an underwater acoustic communication link and at least a base buoy and one remote buoy with acoustic transponders and GPS position locating equipment. The location of the buoys is determined by the GPS equipment. The underwater diver or vehicle each carries an acoustic tracking unit transponder which emits a tracking unit message specifying its identity and its last known position at an assigned time slot. Upon reception of the tracking unit message by the base buoy, an acoustic base buoy message is emitted which includes the buoy position. The tracking unit receives the base buoy message, and marks the time of arrival to determine the propagation delay between the tracking unit and the base buoy. A predetermined delay after the receipt of the tracking unit message by the remote buoy, it sends an acoustic remote buoy message specifying its location.

Abstract: An underwater local area network for oceanographic observation and data acquisition includes a network node for telemetering data to a final destination and a plurality of sensors each of the sensors having an acoustic modem to transmit information to the network node.

Abstract: An underwater acoustic communications system utilizes phase coherent modulation and demodulation in which high data rates are achieved through the use of rapid Doppler removal, a specialized sample timing control technique and decision feedback equalization including feedforward and feedback equalizers. The combined use of these techniques drammatically increases data rates by one and sometimes two orders of magnitude over traditional FSK systems by sucessfully combating fading and multipath problems associated with a rapidly changing underwater acoustic channel that produce intersymbol interference and make timing optimization for the sampling of incomming data impossible.

Abstract: A hydrophone analog signal data acquisition, A/D conversion and data transsion system includes a first-stage signal processing subsystem which provides digital representations of the hydrophone analog signal, which in turn are signal processed for transmission in the form of data packets by a second stage signal processing subsystem (40). Subsystem 40 includes a plurality of Data Multiplexer/FIFO units (48), including corresponding selectively acting data unit accumulators, each accumulator having a plurality of inputs coupled to output channels of the first-stage signal processing subsystem for receiving digital representations of hydrophone analog signals. Each data unit accumulator includes a first buffer (48-2) for storing information that includes a digital representation of the analog hydrophone signal, an identification of a hydrophone that generated the acoustic information, and a time that the acoustic information is received from the hydrophone.

Abstract: A signaling apparatus for generating an audible sound includes a housing containing a cylindrical chamber having two ends, an end member secured over each end, and a projectile member contained within the cylindrical chamber. The projectile member preferably has an outer diameter slightly smaller than the inner diameter of the cylindrical chamber, for limiting lateral movement of the projectile member. The end members form a water-tight seal with the housing to keep moisture out of the cylindrical chamber. The projectile member is preferably a metal ball. The end members have outer surfaces and optionally include a loop attached to the outer surface of one of the end members for receiving a cord. The housing, including the end members, is preferably made of PVC, brightly colored and fluorescent so that the apparatus can be more readily seen in murky water. A foam sleeve is preferably provided over the housing for improving the grip of a person holding the device.

Abstract: A dive profile recorder for monitoring conditions encountered by a diver under water includes a plurality of transducers to be carried by a diver for generating electrical signals representative of the conditions encountered by the diver. Encoding circuitry electrically connected to the transducers encodes the electrical signals to form a serial data stream and a transmitter electrically connected to the encoding circuitry transmits the serial data stream through the water. A receiver remote from the diver receives the transmitted serial data stream and decoding circuitry electrically connected to the receiver decodes the serial data stream to electrical signals representative of the conditions encountered by the diver. A display electrically connected to the decoding circuitry receives the electrical signals and displays human-perceptible indicia of the conditions encountered by the diver in response to the received electrical signals.

Abstract: A system for measuring the speed in water of an underwater towed array has towbody connected in close proximity to the array by means of a rope drogue. The towbody has a freely turning propeller that turns a shaft that has a rotor magnet. Magnetic pulses from the rotor magnet are converted first to an electrical and then to an acoustical signal. The acoustical signal from the towbody is received by the towed array and converted back to an electrical signal that is transmitted along a line to a ship that is towing the array. The ship then displays the detected speed and/or utilizes the information received for control purposes.

Abstract: A uniquely designed acoustic transducer comprising a stack of piezoceramic elements (other piezoelectric materials may be used) mounted upon a tuned, shaped transmit/receive head made of hardened metal alloy. The ceramic stack is preloaded to the head via a stress bolt. Insulator electrodes used in the ceramic stack are selected to minimize compliance in the stack for maximum efficiency. All the material properties, sizes, weights, etc., as well as the overall transducer design are carefully selected to act in combination to match the impedance of the load (i.e. metal structural framework). The diameter of the tip of the tuned, shaped driving head is sized such that when clamped to a metal framework, the base metal of the material just under the tip is compressed to or slightly beyond its yield point. This eliminates the requirement for surface preparation because any coatings will be displaced under the applied pressure and any surface irregularities will be flattened out.

Abstract: When a signal from a calling device is received by a remote-located fishfinder, the fishfinder emits supersonic waves to a body of water below it and receives reflected waves from a fish shoal as an analog signal. Fish shoal information is expressed by the varying amplitude of the voltage of the signal. The analog signal is converted to Morse code form and sent to the calling device. The Morse signal received by the calling device is converted to the fishfinding information to be displayed. In the transmission procedure in the system of the present invention, analog signals of fish-shoal information are successively converted from analog to digital form. The signals are also converted to respective fish-shoal pulse signals divided on the basis of a given periodical synchronizing pulse and added. The fish-shoal information data are then sampled at predetermined intervals for a plurality of unit signal amplitudes determined along the time base. The data are ordered with bit units and stored in the memory.

Abstract: Apparatus and method for transmitting and receiving hydroacoustic pulses used to determine the spatial separations between pairs of such apparatus. According to a preferred embodiment, the apparatus transmits hydroacoustic pulses having a selected shape and frequency at specific times and also determines the time of arrival of received hydroacoustic pulses having a known shape and carrier frequency. Included is a transducer for converting the hydroacoustic energy received from a body of water into electrical energy and for converting electric pulses into hydroacoustic pulses which are then coupled into the body of water. Electric pulses having a selected shape and carrier frequency are digitally synthesized in response to a count comparator.

Abstract: A digital underwater communication system includes a transmitter and a receiver. An oscillator bank in the transmitter generates a plurality of signals, each having a unique frequency. A timed switching matrix selects predetermined combinations of signals from this plurality and a gate passes only those signals within a selected combination that corresponds to the binary value of a bit to be transmitted. A timer commands the switching matrix to select different combinations at each bit time. The receiver contains a filter bank feeding a plurality of channels, each responsive to a different one of a plurality of signals generated in the oscillator bank. A receiver timer, synchronized with the transmitter timer, enables combinations of receiving channels corresponding to the combinations of signals selected by the transmitter switching matrix during that bit time.

Abstract: An underwater communication system provides reliable underwater transmission of digitally encoded communications as a series of consecutive acoustic frequency pulses (40) wherein the frequency of each pulse corresponds to one of two preselected frequency settings (F.sub.A,F.sub.B). A communication is transmitted as a series of frequency pulses (40) divided into a header section (44), a message section (45), and a parity bit (46). The header bits are of a first pulse width (T1), and the message and parity bits are of a second pulse width (T2). Received communications are converted into an electrical receive signal by a hydrophone (76), which is processed by a sonar control (61) and provided to a CPU (62) which decodes the communication for display on a display unit (60).

Abstract: The present invention relates to an underwater detection system which radiates ultrasonic wave search signals by a transmitter disposed at a first point in the water, receives echo signals resulting from the search signals to detect underwater conditions, transmits information representative of underwater conditions to a second point spaced from the first point, and receives and displays the information representative of underwater conditions by a receiving transducer and an indicator. The transmitter disposed at the first point has a transmission side memory for storing echo signals, a device for writing the echo signals into the transmission side memory at periods which become longer as time elapses from an instant at which an ultrasonic wave search signal is radiated and for reading the stored echo signals out of the transmission side memory at constant periods.

Abstract: Apparatus and process for providing a communication link between separate submersibles and, in particularly, for providing communication between a launched submersible and a host submersible. A thread of polyelectrolytic material is provided in electrical communication with a launched submersible prior to launch and payed out and stretched as the launched submersible extends a distance from the host submersible to permit secure communication between the submersible, transmission of command signals for guidance and arming/disarming, from the host to the launched submersible, and to receive data from deployed sensors. The conductive thread includes an organic solvent having dispersed therein a first polymer consisting of a water insoluble polymer that serves as the conductive polymer backbone and a second polymer consisting of a semi-water soluble high molecular weight polymer that effectively surrounds the conductive polymer backbone.

Abstract: An acoustic data acquisition system for shipboard use is disclosed that allows for underwater acoustic data measurements at preselected submerged marine structural coordinates using a free swimming, quiet dynamically positionable remotely operated vehicle (ROV). Moreover, the disclosure provides a method of performing acoustic data acquisition with an ROV by first inputting the marine structural features by use of a computer aided design subsystem, determining the required trajectory path and hovering coordinates for data measurements, next, establishing the acoustic telemetry system for the remotely operated vehicle's control system to operate within and make an absolute positional fix to the marine structure's coordinates then, establish the ambient acoustic conditions of the worksite. The system is monitored and controlled from a computer based system.

Abstract: An acoustic, underwater, telemetry system between two vehicles, a free-rung, deep-operating, sonar platform, or Sonaray vehicle, to overcome refraction, and a surface ship to provide processing of the sonar data gathered by the Sonaray vehicle. The telemetry system is required to communicate analog sonar information, digital command to control the platform, and digital information concerning the status of the platform, between the Sonaray vehicle and the surface ship. The Sonaray concept requires more than 32 channels of analog information for sonar data transmission, each corresponding to a particular received azimuthal beam and each having an information bandwidth of 1 kHz. The output of the analog channels consists of raw data from the search sonar. Because of the long range and very high reliability of the transmission required for the status and control channels, sonar processing by cross-correlation is used to search in both range and doppler.

Abstract: An underwater acoustic communication system provides an operator with adjable frequency diversity so that data rates may be tailored to specific multipath environments. Transmitted messages are sent with precursor transmission/reception synchronization data and transmission parameter data so that the receiving communication end will recognize when message data starts, tone length as-well-as the frequency diversity of the transmitted message. Timing is extracted from the data to compensate for Doppler shift.

Abstract: A dive parameter transmitter/receiver assembly for scuba diving includes a transmitter circuit with a control unit with one or more sensors for detecting dive parameters and/or information to be displayed. A modulator is included for modulating the parameter(s) or information and a transmitting transducer for propagating the parameter(s) or information. A receiver circuit is included and has a receiver transducer a demodulator, a decoder and a display for displaying the parameter(s) or information.

Abstract: An underwater location beacon emits a continuous wave signal which is phase-shift modulated by a pseudo-noise, spread spectrum code. This signal is detected with an exact replica of the transmitted code. To an unauthorized observer without the replica, the transponder's signal is indistinguishable from background ocean noise. The spread spectrum code allows extraction of the signal from high levels of ocean noise, providing an increased detection range, jamming resistance, covertness, and unique signals for each pinger. The outputs of the surface spread spectrum receiver are used with automated location algorithms. Several receivers at different surface positions provide the underwater coordinates of the pinger's location.

Abstract: A dive parameter transmitter/receiver assembly for scuba diving includes a transmitter circuit with a control unit with one or more sensors for detecting dive parameters and/or information to be displayed. A modulator is included for modulating the parameter(s) or information and a transmitting transducer for propagating the parameter(s) or information. A receiver circuit is included and has a receiver transducer, a demodulator, a decoder, and a display for displaying the parameter(s) or information.

Abstract: Apparatus for monitoring the laying of a deep sea cable or flexible pipeline (1) from a vessel (22). The apparatus comprises a sleeve threaded on the cable or flexible pipeline and having sliding means (4) tangential to said cable or pipeline and measuring means (3A) for measuring variables indicative of the position of the sleeve and for transmitting their values, positive buoyancy means (8) mechanically connected to the sleeve, an auxiliary small chain (19) suspended from the sleeve and extending down to the sea bed, the mass per unit length of the chain, and the masses and volumes of the sleeve and of the positive buoyancy means being such that the sleeve is maintained around that part of the cable which is situated at a substantially constant height above the sea bed (21), which height is relatively small compared with the depth of the sea bed.

Abstract: A process is provided for transmitting a signal, without material connection, through a conducting wall which may be a ship's hull, to external user apparatus.A current supplied by a generator and whose intensity is proportional to the amplitude of the signal to be transmitted is applied between two points on the hull. The magnetic field variations generated by the passage of the current are detected by a sensor on the other side of the hull and, suitably amplified, are used for controlling an apparatus.

Abstract: A method and apparatus for measuring electrical or magnetic fields, such as high-frequency alternating fields in a nuclear magnetic resonance tomography device, convert a test signal into a corresponding ultrasound signal, and transmit the ultrasound signal to a receiver, where the received signal is converted back into an electrical signal. The transmission path contains no metallic components and thus does not cause any disturbance in the field being measured.

Abstract: A precision Doppler effect compensator provides Doppler compensation in astic transmission by simultaneously sending a known reference signal with an information signal. The information signal and reference signal undergo identical Doppler effects. The compensator uses the Doppler shifted reference signal to sample the analog Doppler affected information signal. The analog information signals are digitally converted and stored in a first in first out shift register. The samples are read out of the FIFO at a rate corresponding to the frequency of a non-Doppler shifted reference signal so as to precisely reconstruct the information signal as transmitted. The samples read from the FIFO are reconverted from digital to analog form to be presented to a receiving modem for further information processing.

Abstract: A rate of ascent monitor for drivers uses a sound transducer with velocity characteristics, preferably a diaphragm type piezoelectric transducer, to sense rate of pressure change, and a threshold detector connected to the transducer to drive an indicator providing a warning of an excessive rate of ascent. A second threshold detector can be used to discriminate between descending and ascending motion. The device can be a compact wrist mounted unit.

Abstract: An underwater sensing system has a trunk cable that transmits a plurality clock signals from its first end to its second end. A plurality of signal handling nodes are installed successively along the trunk cable in a spaced apart relationship. Each of a plurality of linear sensor arrays extend from one signal handling node. Each sensor in the sensor arrays receives the clock signals and generates a data output signal in response thereto at specifically ordered time sampled intervals based on a count of the clock signals. The data output signals are transmitted to the one signal handling node associated with the sensor array. At each of the signal handling nodes, a multiplexer interleaves the data output signals received from its sensor array in a continual throughput, time-division multiplexed fashion with concatenated data output signals received from the next successive signal handling node located further from the first end of the trunk cable.