Abstract: A multimode wireless communications system that uses the three mechanisms of light, radio and acoustic carriers either in combination or through selection of the most appropriate carrier.

Abstract: A system and method is provided for using acoustical pulses generated from an airborne laser source to locate objects under water. An array of acoustic sensors, such as passive sonobuoys at the ocean surface, is deployed in known or determinable locations by aircraft. Each area surrounded by acoustic sensors comprises a search cell, within which sonar scattering data can be used to locate objects. Following sonobuoy deployment, the aircraft uses the laser to rapidly generate many laser-acoustic pulse sources within each search cell, which in turn generate spherical acoustic pulses traveling through the water. The acoustic sensors receive the acoustic pulses, either on a direct path or on a scattered path after the pulse strikes an underwater object. The sensors record the acoustic signatures of the received pulses and transmit data of the recorded acoustic pulses to a processor such as processor on a nearby ship.

Abstract: A sound collection environment deciding device for deciding whether the sound was collected in air or in water by utilizing an audio signal of collected sound is provided. Methods of Utilizing the audio signal of collected sound include, for instance, utilizing a difference of frequency characteristics between in-air and in-water of the audio signal of collected sound, utilizing a difference of propagation characteristics between in-air and in-water of the audio signal of collected sound, or the like.

Abstract: Disclosed herein are systems for housing an electronic audio device in harsh environments including aquatic and rugged environments. In one embodiment, a system is disclosed for allowing a user to control an audio device having a capacitive touch sensitive control feature from outside of a waterproof housing.

Abstract: An underwater operations support system facilitates underwater exploration, monitoring, maintenance and construction operations associated with development of natural resources. The operations support system may include energy generation subsystems, energy accumulation subsystems, communication subsystems, docking stations, repair and maintenance robots, housings for divers, and video subsystems. Supported equipment includes ROVs, HROVs, AUVs, and other autonomous and semi-autonomous mobile robots which move materials, perform manual tasks, and survey the environment. Operational efficiency is enhanced by recharging, repairing and reconfiguring vehicles, and transferring data and commands between vehicles and a control station, without moving the vehicle to and from the surface, and without need for a surface ship to remain on site for the duration of operations.

Abstract: A system and method for signal distribution within a sensor array uses a coaxial transmission line. Taps are affixed to the outer conductor of the coaxial transmission line and include field coupling portions extending into the internal field region of the coaxial transmission line. Electromagnetic energy propagating within the transmission line can be extracted to power the sensors. Sensor signals can be modulated onto radio frequency signals and propagated along the transmission line to distribute the sensor signals.

Abstract: The present invention provides a navigation system for an unmanned underwater vehicle that includes at least two navigation sensors that provide latitude and longitude measurements of unequal accuracy, a processor and a memory. The memory stores a machine-readable set of instructions executable by the processor to process the latitude and longitude measurements received from the navigation sensors, and to estimate vehicle latitude and longitude with approximately equal accuracy.

Abstract: An unmanned underwater vehicle for use in water and with at least one acoustic signal source includes a vehicle body, a steering mechanism to direct the vehicle body through the water, a propulsion device to force the vehicle body through the water, and an adaptive Doppler guidance and control (ADGC) system. The ADGC system is configured to receive acoustic signals from the at least one acoustic signal source and to control the steering mechanism using changes in at least one frequency component of the received acoustic signals caused by Doppler shifts.

Abstract: A method to detect data transmitted from multiple antennas, said method comprising steps of: selecting a starting data block and calling it as previous data block; defining a set of indices of bits to be checked for possible flip in the previous data block as a check candidate set; applying update rule to obtain updated data block using the previous data block and the check candidate set, wherein the update is made in such a manner that change in likelihood is positive; checking if the updated data block and several consecutive previous data blocks are the same; if yes, declare the updated data block as the detected data block; if no, make updated data block as previous data block and repeat updation of data block. FIG.

Abstract: An underwater vehicle including an axi-symmetric framing system rotatable about a centerline to define a shell of revolution having a uniformly-convex outer boundary. A narrow-beam sonar array is mounted on the axi-symmetric framing system, and includes a multitude of simultaneously-fireable and/or asynchronously-fireable transducers distributed substantially evenly over a 4?-steradian viewing angle. The present invention provides the necessary configuration for a vehicle wherein an internal algorithm can compare a “new” geometry to an “old” geometry collected earlier to construct a best fit of the new world map with the old world map and locate the vehicle within the context of the new world map. This then provides a completely independent mechanism for correction of the gradual drift in x and y that is not dependent on any form of external navigation aid.

Abstract: A directional microphone system is disclosed, which comprises circuitry for low pass filtering a first order signal, and circuitry for high pass filtering a second order signal. The system further comprises circuitry for summing the low pass filtered first order signal and the high pass filtered second order signal. A method of determining whether a plurality of microphones have sufficiently matched frequency response characteristics to be used in a multi-order directional microphone array is also disclosed. For a microphone array having at least three microphones, wherein one of the microphones is disposed between the other of the microphones, a method of determining the arrangement of the microphones in the array is also disclosed.

Abstract: A matched-field based sonar system and method of use that supports real-time, three-dimensional acoustic source localization using a mobile, horizontal array. The system receives and processes acoustic array, non-acoustic array, and own-ship navigational data in the matched-field process (MFP). Driven by own-ship and array status, a global bathymetry database and an acoustic environmental model are used to generate replicas for the MFP. If a three-dimensional tracker is assigned, then the tracker will steer the search region to maintain contact on the target of interest. Displays are provided to the user including tracker displays (which provide tracker information), MFP ambiguity surface displays (which support contact localization), and non-acoustic and navigational displays. A control interface allows a user to control the search region in bearing, range, depth, and frequency; assign the three-dimensional tracker function; and control display processing.

Abstract: An automatic diver identification unit for providing motorized and multi-directional surface movement relative to a position of an underwater diver and to identify the position of a diver at the surface of a body of water. The automatic diver identification unit includes a buoyant main body portion having at least one interior chamber. An electronic control system is included within the automatic diver identification unit, and includes a diver movement detection switch. The unit operates to provide automated adjustment of a dive line relative to a signal received indicating the depth of the underwater diver. A propulsion means interconnected with the electronic control system identifies movement of the underwater diver and positions the unit above the diver. An identification signal identifies the location of the unit to other persons at the surface of a body of water.

Abstract: An underwater detection apparatus for detecting a target by transmitting and receiving an ultrasound signal is provided. The apparatus includes a replica memory module for storing the typical amplitude evolution of a seawall echo during a predetermined time period as a template-replica beforehand, a correlator module for determining a correlation between the amplitude evolution of an echo signal reflected from the target and the template-replica, a seawall detector module for detecting a seawall position based on the correlation, and a seawall display processor module for displaying the seawall on its position in an indicator.

Abstract: The survey technique for use in a marine environment to survey a subterranean structure includes providing an arrangement of plural signal sources in a body of water to produce corresponding signals. The signals of the signal sources in the arrangement are set to cause reduction of at least one predetermined signal component in data received by a receiver in response to the signals.

Abstract: An unmanned underwater vehicle for use in water and with at least one acoustic signal source includes a vehicle body, a steering mechanism to direct the vehicle body through the water, a propulsion device to force the vehicle body through the water, and an adaptive Doppler guidance and control (ADGC) system. The ADGC system is configured to receive acoustic signals from the at least one acoustic signal source and to control the steering mechanism using changes in at least one frequency component of the received acoustic signals caused by Doppler shifts.

Abstract: A submersible electronics device for use in a body of water and a substratum floor below the body of water includes a submersible housing, an operational electronics system, and a mobility system. The operational electronics system is mounted in and/or on the housing. The operational electronics system is adapted to communicate with another device and/or to sense at least one of a physical signal and an environmental parameter. The mobility system is selectively operable to fluidize the substratum, vibrate the housing, and/or adjust a buoyancy of the submersible electronics device to selectively move the housing into the substratum to at least partially bury the housing in the substratum and/or to selectively move the housing out of the substratum to at least partially unbury the housing from the substratum.

Abstract: An ultrasonic surveying method includes a network of transceivers adjacent the item to be surveyed to establish a reference plane and locating an array of pingers on the object to be surveyed to establish a survey plane, establishing by ranging from the pingers to the network the location of the survey plane, detecting relative motion between the network and the pingers and correcting survey measurements for the detected motion.

Abstract: A software system and method is presented that calculates the sensor directivity at all spatial angles, and stores these values in a two dimensional matrix. These values are then used as additional “weighting” coefficients in the equation for the pressure detected by an array of directive sensors. The azimuthal and polar angles of a particular sensor normal vector are used to “rotate” the sensor directivity matrix to account for the angular orientation of each sensor within the array. The software system receives as input sensor and array geometry, shading functions, sensor shape, array structure baffling, steering, and shading. A sensor can have the shape of a point, line, plane, volume, baffled ring, or circular plane piston. The sensors within the array can either be baffled by the array structure or retain their free field directivity response, and array as a whole can have steering or no steering.

Abstract: An array of three-axis magnetometers used for dynamic magnetic anomaly compensation are located at the corners of a parallelopiped, with pairs of magnetometer outputs used to derive a magnetic anomaly gradient vector used to compensate a compass and/or the output of a gyroscope in an inertial management unit. The system may be used in a neutrally buoyant remotely operated vehicle to permit ascertaining of course and position in the absence of surface control signals.

Abstract: Invention relates to a novel method of and system for ranging between an acoustic source carried on an unmanned or autonomous undersea mobile vehicle (UUV or AUV) and preferably a plurality of hydrophone receivers remotely deployed from the vehicle in predetermined patterns, generally suspended from sonobuoys equipped with above-the-sea relay radio transmitting antennas, and with time synchronization provided amongst the source and the receivers, wherein the time delay from the transmissions of the source is measured by utilizing special signal processing, enabling range to be measured in close to real time by determining the product of the sound velocity and the measured time delay, and with the process continually and periodically being repeated throughout the duration of the vehicle run.

Abstract: Seabed sensor units, systems including same, and methods for acquiring seabed data are described, one seabed sensor unit comprising a base, the base containing at least one sensor able to detect a seismic signal, electronics comprising a clock and one or more electronic components enabling the sensor to communicate seismic data to one or more memory modules, and a local autonomous power source. This abstract is provided to comply with the rules requiring an abstract, which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. 37 CFR 1.72(b).

Abstract: A system for locating a diver is provided. The system includes a diver module for association with a diver that is capable of producing both an audible frequency signal to assist in locating the diver while submerged, and a radio frequency signal to assist in locating the diver when surfaced. In addition, the diver module includes a switch to enable the initiation of an active mode of the diver module. The diver module may also include a receiver visual display to indicate the direction to another diver module or to a boat module. The location signal boat module provides a boat operator with an indication of the direction from which a location signal is being received.

Abstract: Seismic sensor systems and sensor station topologies, as well as corresponding cable and sensor station components, manufacturing and deployment techniques are provided. For some embodiments, networks of optical ocean bottom seismic (OBS) stations are provided, in which sensor stations are efficiently deployed in a modular fashion as series of array cable modules deployed along a multi-fiber cable.

Abstract: A seabed resource exploration system includes: a vibrator 1 for transmitting a sound wave into the sea and receiving a scattered wave in which the sound wave is reflected on a boundary surface between seawater and a mixture of methane gas and methane hydrate, which exists in the seawater; and an analyzer 17 for determining that the methane hydrate exists in a seabed immediately under the mixture when backscattering strength, calculated by the transmitted sound wave and the received scattered wave, is in a predetermined relationship. The predetermined relationship satisfies a relationship that a maximum value of the backscattering strength is ?60 to ?30 dB and an average value of the backscattering strength is ?70 to ?50 dB. The backscattering strength is on a grid obtained by cutting the mixture into round slices in the depth direction by a predetermined width, in a range from the seabed to a predetermined height.

Abstract: An underwater RF signal propagation path is created by utilizing a plurality of individual RF transceivers such as MEMS RF transceivers. Each MEMS RF transceiver has a predetermined buoyancy. A stream of the RF transceivers are released to form a line of RF transceivers underwater such that the individual RF transceivers have an RF transmission and reception distance greater than the distance between the RF transceivers whereby an RF signal can be repeatedly retransmitted down the line of RF transceivers.

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: An imaging sonar system develops three-dimensional images of the space below, to the sides, and forward of a ship relative to a fixed frame of reference. Various features permit the system to be used in non-military environments and make possible low cost with substantial capabilities.

Abstract: The present invention relates to an improved autonomous node seismic recording device having an integrated modular design and one or more features that assist coupling of the unit to the sea floor in order to improve the vector fidelity of seismic signal measurement.

Abstract: A sonar dome having an acoustic array housed therein. A plurality of bubbles are generated within the fluid inside the sonar dome. The generated bubbles are of an amount and size to reduce the speed of sound within the sonar dome fluid. Reduction of the speed of sound within the sonar dome fluid effectively increases the aperture of the acoustic array. The bubbles can be generated from a gas source or electrolytically. Typically, each individual bubble is less than 0.01 mm in diameter to reduce bubble velocity in the fluid.

Abstract: A diver unit computes the direction and distance to a specified target. When the target is obstructed, the diver unit receives navigation assistance data from another diver unit. The navigation assistance data includes direction information that is referenced to a common reference line extending between the two diver units.

Abstract: An underwater sounding apparatus includes a transducer transmitting an acoustic sounding beam along a plurality of directional surfaces that intersect in three-dimensions and receiving echoes returning from within a fish school using receiving beams. The transducer can form the receiving beams in directions generally along a substantially vertical planar directional surface and in directions generally along a substantially umbrella-shaped directional surface formed around the ship, the umbrella-shaped directional surface intersecting both a horizontal plane and the vertical, planar directional surface. A signal processing section calculates fish quantity information about the fish school by constructing pseudo-three-dimensional data from data obtained by the receiving beam. Also, the signal processing section may binarize the data obtained by the receiving beams and calculates an approximate value of the volume of the fish school by constructing pseudo-three-dimensional data from the binarized data.

Abstract: The present invention provides a navigation system for an unmanned underwater vehicle that includes at least two navigation sensors that provide latitude and longitude measurements of unequal accuracy, a processor and a memory. The memory stores a machine-readable set of instructions executable by the processor to process the latitude and longitude measurements received from the navigation sensors, and to estimate vehicle latitude and longitude with approximately equal accuracy.

Abstract: A protective enclosure is disclosed for an interactive flat-panel control device. The protective enclosure is watertight, crush-resistant, and impact-resistant. An electrical adapter may disposed within the protective enclosure and covered with an elastomeric covering that permits a connector of the adapter to flex with respect to the lower shell of the enclosure so that the connector may easily be inserted into an interface jack of the electronic device. The elastomeric covering also provides a watertight seal that enables the protective enclosure to be submersibly watertight. While providing protection, the protective enclosure simultaneously allows smooth and accurate interaction with the interactive flat-panel controlled device. The protective enclosure has a protective membrane that permits RF and touch screen stylus inputs, as well as capacitance, such as from a finger, to be transmitted accurately to the flat-panel control.

Abstract: A system and method for estimating the SNR in a sonar environment and for determining the effect of the estimated SNR on sonar ranging accuracy. The system includes a sensor, a transmitter, a receiver, a plurality of band-pass filters, a cross correlator, and a data analyzer. The transmitter transmits a first signal having a predetermined frequency range through a transmission medium. The sensor generates a second signal corresponding to an echo signal reflected from an object. The first and second signals are provided to the band-pass filters, each operative to pass a respective sub-band of frequencies. The filters provide filtered versions of the first and second signals to the cross correlator, which performs cross correlation operations on the filtered signals. A data analyzer analyzes the cross correlator output data to determine the variability of cross correlation peaks within each frequency sub-band, thereby allowing more accurate SNR estimations in noisy environments.

Abstract: A navigation processor is interfaced to an acoustic processor and to DGPS surface positioning equipment on a vessel. The navigation processor receives (a) position data from the DGPS surface positioning equipment, (b) data from a gyrocompass on an underwater system, (c) depth data of the underwater system, (d) velocity data of the underwater system based on data from a Doppler log unit on board the underwater system, and (e) range and bearing data of the underwater system from the acoustic processor, in order to calculate coordinates of the underwater system.

Abstract: The sonar device includes a sonar transducer, a noise filter, a microprocessor and an output device. The system warns the user when a hazardous objects is detected or when signals from companions decrease. The portable sonar device can be built into various watersport devices including scuba diving equipment, surfboards and windsurfboards.

Abstract: A submersible, waterproof enclosure for a portable audio device is disclosed. Also disclosed is a removable lid allowing for the inserting and removing of the device from the enclosure. The disclosure further provides a connector system and an audio communication link connecting the housing to a device capable of generating sound, and to a device capable of producing sound while being submerged in an aquatic environment. Also disclosed are headsets containing at least one speaker within a waterproof enclosure. The speakers may be positioned in or near the ear canal, and attached to the ear or to the user's equipment. The headsets may further comprise devices for controlling power and fidelity. The disclosed invention provides an affordable, easy to use and flexible appliance for utilizing an audio device while being submerged into an aquatic environment.

Abstract: An exemplary housing mechanism (8) for an electronic device includes a cover (10) and a frame (20). The cover has a cover body (11), a sealing element (12), and a sidewall (13) formed around the cover body. A surface of a distal end of the sidewall is recessed thereby forming a receiving slot (16) therein. The sealing element has a connecting portion (122) and a positioning portion (124) connected to the connecting portion. The connecting portion is fixedly received in the receiving slot of the cover. The frame has a positioning slot (26) defined therein and the positioning portion of the sealing element is for reception in the positioning slot of the frame when the cover is closed to the frame.

Abstract: Methods and apparatuses process signals. The method according to one aspect of the present invention receives a first signal; obtains a second signal and a third signal from the first signal, wherein a gain of the second signal is smaller than a gain of the third signal; detects saturation in the third signal; and generates a composite signal from the second signal and the third signal, the step of generating a composite signal including selecting a part of the second signal for the composite signal, when the detecting step detects saturation in the third signal, and selecting a part of the third signal for the composite signal, when the detecting step does not detect saturation in the third signal.

Abstract: Methods and apparatus determine if an underwater intruder passes under a protective boundary. A sonar sensor system comprises a plurality of sonar sensor modules that are spaced on a protective boundary. A sonar sensor module comprises a sonar transducer (sonar array) that is characterized by an omni-directional radiation pattern that may overlap an omni-directional radiation pattern of an adjacent sonar sensor module transducer. The sonar sensor module collects sonar data such as range information of the target in relation to time. A central processor obtains the sonar data from each sonar module through a telemetry link. The central processor processes the sonar data from the plurality of sonar sensor modules in order to determine an estimated path of the target and may determine if the target should be considered as a threatening underwater intruder from a calculated threat level estimate based on this data.

Abstract: A system and method of performing sonar range estimations in a noisy sonar environment. The system includes a sensor, a transmitter, a receiver, a plurality of band-pass filters, a cross correlator, and a data analyzer. The transmitter transmits a pulse through a transmission medium. The pulse travels through the transmission medium until it strikes an object, which returns an echo to the sensor. The sensor provides the echo to the receiver, which provides an indication of the echo to the band-pass filters. The respective band-pass filters provide filtered versions of the echo and pulse to the cross correlator, which performs multiple cross correlation operations on the filtered echo and pulse. The cross correlator provides output data to the data analyzer, which uses the data to estimate the SNR in the environment and to determine a pulse center frequency corresponding to the estimated SNR.

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: A diving suit and environmental detecting system includes a diving suit and aspirating assembly includes a torso portion, a first arm portion, a second arm portion, a first leg portion, a second leg portion, a head covering, a first glove, a facemask, a second glove and an air tank. A housing is mounted on the first glove. A display is mounted in the facemask. A processor is positioned within the housing and is electrically coupled to the display. The processor is adapted for receiving a plurality of input signals and altering the display based upon the input signals. A power supply is mounted on the diving suit and is electrically coupled to the processor. A locating assembly is electrically coupled to the processor and is adapted for determining a location of the diving suit with respect to a trasmitter and displaying the location on the display.

Abstract: An exemplary apparatus includes one or more “communicators” that are worn, carried by, or otherwise associated with a person or location in an environment. Each communicator includes a synchronizable clock and a transmitter configured to transmit a message including a respective time stamp that is based on a time determined by the synchronizable clock. The message can be transmitted acoustically or in another manner such as by RF signal, optical signal, etc. The clock can be synchronized based on, e.g., a standard clock, another synchronizable clock associated with one or more transceivers, or a selected transceiver. The time stamp can be digital or analog, and can be configured to permit estimation of distance and bearing between synchronized communicators.

Abstract: A system and method for predicting passive, high-frequency sonar array performance at any underwater location, implemented as a software package running on a computer. An operator selects an arbitrary geographical location, specifies a sonar array and defines a target. The necessary bathymetry, and associated oceanographic, environmental and meteorological data are automatically acquired or generated, along with appropriate models for ocean surface and bottom reflectivity, and vertical noise directionality. A Comprehensive Acoustic System Simulation (CASS) software module performs appropriate ray tracing, which is used to produce Cross-Spectral Density (CSD) matrices for the target and the anisotropic ambient noise. These are used to generate graphic and numeric representations of the array's performance at the selected location. A time of year may also be specified and the appropriate anisotropic noise field for conditions expected at that location at that time of year will be generated.

Abstract: A protective enclosure is disclosed for an interactive flat-panel control device. The protective enclosure is watertight, crush-resistant, and impact-resistant. An electrical adapter may disposed within the protective enclosure and covered with an elastomeric covering that permits a connector of the adapter to flex with respect to the lower shell of the enclosure so that the connector may easily be inserted into an interface jack of the electronic device. The elastomeric covering also provides a watertight seal that enables the protective enclosure to be submersibly watertight. While providing protection, the protective enclosure simultaneously allows smooth and accurate interaction with the interactive flat-panel controlled device. The protective enclosure has a protective membrane that permits RF and touch screen stylus inputs, as well as capacitance, such as from a finger, to be transmitted accurately to the flat-panel control.

Abstract: Arrangement with an acoustic array with a sound velocity meter, suitable to be arranged under water. The acoustic array is able to receive acoustic signals from an underwater device and to provide acoustic array output data to a processing arrangement such that the processing arrangement can perform in real-time, a calculation of a position of the underwater device relative to the acoustic array based on the acoustic array output data. The sound velocity meter is able to measure velocity of sound in fluid layers just below a vessel floating on the water and to provide sound velocity meter output data to the processing arrangement such that the processing arrangement can correct the calculation of the position of the underwater device based on the sound velocity meter output data in real-time.

Abstract: While keeping a propeller located in a negative direction of a y-axis turning, transmission of acoustic waves from vibrating elements of a transducer unit is interrupted. Reference signals “A” and “B” which are receiving beam signals having principal acoustic axes oriented in a propeller direction are generated from received signals obtained by “A” and “B” group vibrating elements, respectively. Next, adjustment factors used for removing propeller noise from received signals obtained by vibrating elements on positive and negative sides of an x-axis are calculated by performing arithmetic operation on time-series data on the received signals obtained by the positive and negative sides vibrating elements and on time-series data on the reference signals “A” and “B”, respectively.

Abstract: The emergency underwater notification device disclosed, one of which would be carried by each diver on a team of divers at a dive site, comprises (a) an activator; (b) one or more primary signal emitters, each of which emits a primary notification signal upon activation of the activator, the primary signal emitter comprising one or more of the following: a light source, a hydrophone, a siren, a speaker, or an acoustic transducer; (c) one or more secondary signal emitters, each of the secondary signal emitters emitting a secondary communication signal upon activation of the activator; (d) a receiver capable of receiving communication signals; (e) one or more tertiary signal emitters, each of the tertiary signal emitters to emit a tertiary communication signal upon receipt by the receiver of either a secondary communication signal or a tertiary communication signal from another notification device; and (f) one or more quaternary signal emitters, each of the quaternary signal emitters to emit a quaternary notifi