Abstract: An underwater transducer system reproduces high-fidelity audio signals underwater, and detects and monitors low levels of sound activity, both adjacent to a body of water such as a swimming pool, and in the water. The system includes an underwater housing for a diaphragm that directly contacts the water, a coil assembly movable within the housing and rigidly connected to the center of the diaphragm by a tubular member of the coil assembly engaging a cylindrical boss portion of the diaphragm. The housing can be suspended by an elongated cord member from a wall coping, or mounted within a wall fixture structure. The system can have a source of illumination, a conduit from the source terminating in the housing on the coil axis proximate the diaphragm, and an optical element sealingly protrudes the diaphragm for transmitting light-amplified illumination into the water.

Abstract: A control system for a revolving door includes an ultrasonic sensor having multiple sensor heads. The door has a housing, and multiple moveable compartments formed by door wings attached to and radially extending from a rotatable axis. The sensors emit energy waves into the housing in bursts, then receive echoes from any objects, including people, in the chambers. The sensors are activated when the door is activated by an authorized user. A controller stores a binary "echo" or "no echo" signal in memory in response to an emitted energy wave. The memory is formed by multiple arrays, each array having a column associated with a particular sensor and used for storing echo signals from a particular ultrasonic burst. Each bit in a column represents incremental ranges of objects from the sensor head, and the controller stores the "echo" or "no echo" signal in an appropriate bit based on the elapsed time from the preceding burst.

Abstract: A safety system for a machine tools having a powered feed table in which ultrasonic transmitters and receivers are arrayed on the leading, trailing and lateral sides of the table establishing moving protected zones so that if an operator enters the zones, the machine is shut down only if the table has moved close to the person in that zone. A failsafe feature causes shutdown in the event of failure of any of the safety system components.

Abstract: At least a bottom layer of a swimming pool is continuously scanned at known time intervals in order to generate successive frames of image data containing the contours of all objects whose size exceeds a predetermined size threshold. Successive frames of image data are compared in order to identify those contours which are common to successive frames and whose displacement from one frame to the next is less than a predetermined threshold. This procedure is repeated over successive frames and, since the time interval between one frame and the next is known, a contour which remains substantially motionless for longer than a predetermined time interval may be detected. Such a contour represents a motionless body, on detection of which an alarm is activated. An apparatus according to the invention includes a sonar detector located at the bottom of the swimming pool for scanning the bottom layer thereof so as to produce image data which is subsequently processed by image-processing means.

Abstract: A method and apparatus for detecting fluid flow behind an acoustically reflective structure using pulse echo techniques which do not depend upon measurement of a Doppler effect. A transducer is provided for generating a high frequency beam of acoustical energy in the form of pulses. The transducer is placed proximate, preferably adjacent, the reflective structure such that the acoustic beam is directed toward such structure. A transducer is also provided for detecting the acoustic reflections of the pulses, proximate the position from which the pulses originated, and generating corresponding electrical signals. An electric circuit is provided for subtracting a pair of acoustic reflection signals separated by a short interval of time to produce a difference signal from which the presence or absence of fluid flow behind the acoustically reflective surface can be determined.

Abstract: A control system for a revolving door includes an ultrasonic sensor having multiple sensor heads. The door has a housing, and multiple moveable compartments formed by door wings attached to and radially extending from a rotatable axis. The sensors emit energy waves into the housing in bursts, then receive echoes from any objects, including people, in the chambers. The sensors are activated when the door is activated by an authorized user. A controller stores a binary "echo" or "no echo" signal in memory in response to an emitted energy wave. The memory is formed by multiple arrays, each array having a column associated with a particular sensor and used for storing echo signals from a particular ultrasonic burst. Each bit in a column represents incremental ranges of objects from the sensors head, and the controller stores the "echo" or "no echo" signal in an appropriate bit based on the elaspsed time from the preceding burst.

Abstract: A continuous wave (CW) leaky cable sensor for an intrusion detector uses a pair of elongated parallel cables, one for establishing an RF field and the other for receiving the field. A modulator is connected at an intermediate location of the receiving (or transmitting) cable, subdividing a detection zone into detection regions on each side of the modulator. The modulator selectively modifies a signal received by a portion of the receiving cable connected to its input. By processing the signal at the output of the receiving cable, the detection region for either side of the modulator in which an intrusion has occurred can be determined. The resolution of a CW sensor is thus increased at low cost. Multiple modulators can be used at spaced locations increasing the number of detection regions, and thus the resolution.

Abstract: A mounting apparatus for the sonic transducer of a directional Doppler fish-finder includes an elongate tubular control arm and a clamp assembly for attaching the control arm to the side of a boat so as to extend along and pivot about a generally vertical axis. The upper end of the control arm includes a pivotally mounted control lever, and the lower end includes a pivotally mounted transducer mounting plate to which the transducer is attachable. The control lever and the mounting plate are interconnected by a pair of cables extending through the tubular control arm, whereby pivotal movement of the control lever causes pivotal movement of the mounting plate about a generally horizontal axis. Pivotal movement of the mounting plate about both the vertical and horizontal axes enables a fisherman to direct the sonic signal of the transducer in a locus of directions representing semispherical coverage of the water about the boat.

Abstract: An automatic ultrasonic system for controlling the filling of different sizes of beverage containers which may or may not contain various quantities of ice. The system includes a transducer assembly and a control module, both preferably connected to a beverage dispenser valve assembly. The transducer assembly includes at least two piezo-electric crystals for separately transmitting and receiving ultrasonic wave energy from the grate, the cup lip, the top of any ice in the cup, and the rising liquid level, and for generating signals corresponding to the travel time of the ultrasonic energy. The control module includes a microcomputer and associated circuitry. The system can include two separate transmitter and receiver crystals, or in a preferred embodiment two transmitter-receiver pairs of crystals.

Abstract: A system for detecting the presence of intruder targets in an area under ar surveillance and in which the number of normal targets may vary, including the processing of gated time sample receiver signals through a first monitoring circuit having a counter and comparator means to develop output signals representing deviation of actual time sample count from a normal reference count, and through a second monitoring circuit including additional counter and count trigger means for developing an alarm signal responsive to continued deviation of actual count from reference count over several actual counts in a time sequence of counts such that normal variation of target number will not produce an alarm signal.

Abstract: An electronic barrier utilizes a bifurcated beam of wave energy to establ a barrier area having a null between the forks thereof. Objects encroaching on said beam cause a portion thereof to be scattered in the foreward direction. Suitable receiver equipment located remote from the source of the bifurcated beam and responsive to the foreward scattered beam is connected to provide an indication of said encroachment.

Abstract: An access alarming method and apparatus for activating an alarm in the event of the access of a working vehicle, such as a road roller, to an object, such as a worker, in the same working area as the vehicle. An ultrasonic wave transmitted by a transmitter on the object is received by a receiver on the vehicle. The received signal is processed and used to determine the relative position of the vehicle with respect to the object. An alarm is activated, and/or the vehicle is braked when it is judged that the object is within a hazard area determined in relation to the position and course of the vehicle.

Abstract: An alarm system monitors a region, and includes a transducer supported to aim toward a boundary of the region. The transducer transmits sonic waves and receives echoes. The system generates an initial value corresponding to the distance between the transducer and a boundary of the region at one time, and activates the transducer at a later time to generate a current value corresponding to the distance between the transducer and a location from which the echoes originate. A control compares the current value to the initial value and activates an alarm when the current value differs significantly from the initial value. In one embodiment of the invention, the transducer aims toward a window of a vehicle and thereby detects either opening of the window or an associated door, breakage of the window, or intrusion into the vehicle between the transducer and the window. Transducers mounted on the underside of a trunk lid and a hood detect lifting the trunk lid or hood, respectively.

Abstract: A movable door incorporates a proximity detection system for sensing obstructions in the path of the door. The system comprises an array of transmitter/receiver pairs (21, 22 and 23), each pair comprising a transmitter (1) for transmitting an energy pulse, a receiver (2) located adjacent the transmitter and directed to receive any reflected transmitter pulses, and a shielding (3) for shielding the receiver (2) from receiving energy pulses directly from the transmitter (1). At least two transmitter/receiver pairs (21, 23) are mounted on a leading edge or face of the door (12) to transmit energy pulses in a direction which is not at right angles to the leading surface or edge of the door, to monitor for obstructions in the path of the door (12). Another two transmitter/receiver pairs (26 and 28) are mounted on the leading edge or surface of the door (12) to transmit energy pulses at right angles to the surface or edge of the door (12).

Abstract: An electromagnetic lock which mounts at the top of a door frame and magnetically bonds with an armature employs both an ultrasonic sensor and a passive infrared sensor to detect the approach of an individual at the doorway. Both the ultrasonic sensor and the passive infrared detector have fan-shaped sensing regions which are positioned forwardly from the doorway. Upon detection of an individual approaching the doorway, the lock is capable of automatically releasing to allow egress through the doorway.

Abstract: A dual sensing intrusion detection system includes a passive infrared radiation detection sensor that generates a first output signal in response to the detection of an intruder in the volume of space. A second detection sensor is directed to the same volume of space and generates a second output signal in response to detection of the intruder. A switch activates the second detection sensor in response to the detection of the intruder by the infrared radiation detector. Logic circuit receives the first and second output signals and produces an alarm signal in response thereto to indicate the detection of the presence of the intruder in the volume of space.

Abstract: An intrusion detector and method of operating the detector is disclosed. The detector comprises a means including an antenna for transmitting spaced pulses of radiation energy of a given frequency throughout a region to be protected. Means are also provided for receiving the radiation energy reflected from the protected region. The reflected radiation energy is received between adjacent spaced transmitted pulses in the form of an AC analog signal at the given frequency, the peaks and valleys of which signal vary in amplitude with time. Means are also provided for allocating a portion of the time occurring between transmitted pulses into a plurality of time segments, each of which segments is long enough to correspond to a plurality of cycles of the analog signal.

Abstract: Target discrimination involves processing of sonar echoes in the time-dom and using features of the targets that the human auditory system uses (time separation and amplitude of echo highlights). Known targets are placed in the water and ensonified by multiple broadband transient signals. Echoes from each of the known targets have time-domain feature data extracted and stored to construct a library of known target features. Unknown targets echoes of transmitted multiple broadband transient signals are received and time-domain feature data is extracted from these. A comparison of the unknown target echo features with the known target echo features provides a discrimination of the unknown target echoes.

Abstract: The invention provides an apparatus and method to confirm or deny the presence of an object within the scan area of an ultrasonic sensing system by requiring that any object be identified on at least two consecutive scans of the sensing system and using scan energy patterns which occur at irregular repetition times to selectively reject spurious direct or reflected signals present in the area. A generator of predetermined pattern burst of ultrasonic energy is arranged to produce one such burst of ultrasonic energy and a timing signal is coupled thereto so as to apply timing signals to cause production of the bursts. The timing signal source produces timing signals only according to a varying pattern whereby separation between adjacent signals meet certain present parameters. The energy patterns are applied to a transmitter which applies them to a scan area whereby the echo or returned energy from an object in the scan area is received and stored.

Abstract: The invention comprises a plurality of monostatic devices for radiating and receiving signals. The monostatic devices are disposed in a vertical spaced relationship such that signals from each device follow a direct path to an object to be detected and a reflected path to the object to be detected. The reflected path includes a path to a surface below the object and a path from the surface to the object. The signals are then reflected from the object and return through both the direct and reflected path. The monostatic devices may be radar antennas or acoustic transmitters.

Abstract: A control method wherein a TV receiver, under the programmed control of a microcomputer, prevents infrared signals from a remote control transmitter and a watch-distance-limit-device transmitter from interferring with each other while using only one time-shared receiver for both functions.

Abstract: A viewing distance sensor for television receiver which cannot influence the remote infra-red control function over other electronic equipment positioned in the vicinity of a television receiver and also cannot be influenced by the infra-red signals transmitted from other electronic equipment. An infra-red signal is transmitted from the infra-red signal transmitter where a viewer is positioned within a viewable distance from the front of television receiver, whereby false operation caused by the infra-red signal from other equipment can be avoided. Also, an inhibiting control signal is applied to the screen controller of a television set where infra-red signals transmitted from other electronic equipments are received by the infra-red receiver in the television receiver, whereby false operation of the viewing distance sensor can be further avoided.

Abstract: An ultrasonic sensor system particularly for automatic door openers of a swinging door type, in addition to sensors (14) for people approaching a door for controlling opening and closing purposes, has at least one microprocessor controlled ultrasonic beam transducer (40, 41) for projecting an expanded unidirectional ultrasonic beam in a selected detection zone in the path of the swinging door and an ultrasonic detector for converting reflected ultrasonic beam energy into an analog electrical signal which constitute an acoustical image of objects in and bounding the selected detection zone. This acoustical image is stored or, a number characterized thereof is stored and this acoustic image is then compared with a later acoustical image of an object in the selected detection zone and then the comparison is used to signal a lack of correlation between the first and second acoustical images to produce a signal preventing operation of the door opening.

Abstract: The interruption demonstrating and multi-phase burglar alarm system is started by signals from 2 or more than 2 detectors amplified and inputted into an interruption demonstrating circuit. By an outside interruption signal, the sensitivity will be properly adjusted. The device also has a multi-phase to detect in single or adjacent multiple areas. The two detectors will be activated within a pre-set period or will not trigger the alarm. The controlling circuit will reset the device in case of any improper or mistaken signals, thereby providing continuous protection and preventing false alarms.

Abstract: An alarm system includes apparatus to be placed in a room to transmit ultrasonic wave signals that rebound off the room's walls and contents, to, and receive the rebounding signals, and to phase balance the transmitted and received signals in order to detect a subsequently unbalance condition caused by a changed in the rebounding signals due to intrusion activity, which produces an electrical alarm signal. Other circuitry responds to reception of an alarm signal to produce an audible or visible alarm. The alarm signal is typically transmitted over electrical power lines.

Abstract: This invention uses an ultrasonic transmitter and receiver and a microprocessor to detect the presence of an object. In the reset mode the invention uses a plurality of echoes from each ultrasonic burst to create a reference table of the echo-burst-signature of the empty monitored environment. The invention then processes the reference table so that it only uses the most reliable data. In the detection mode the invention compares the echo-burst-signature of the present environment with the reference table, detecting an object if there is a consistent difference between the echo-burst-signature of the empty monitored environment recorded in the reference table and the echo-burst-signature of the present environment.

Abstract: An ultrasonic sensor system particularly for automatic door openers of a swinging door type, in addition to sensors (14) for people approaching a door for controlling opening and closing purposes, has at least three microprocessor controlled ultrasonic beam transducer (40, 41, 42) for projecting expanded unidirectional ultrasonic beams in a selected directions in a detection zone in the path of the swinging door and ultrasonic detector for converting reflected single multiple path ultrasonic beam energy into an analog electrical signal which constitute an acoustical image of objects in and bounding the selected detection zone. This acoustical image is stored or, a number characteristic thereof is stored and this acoustic image is then compared with a later acoustical image of an object in the selected detection zone and then the comparison is used to signal a lack of correlation between the first and second acoustical images to produce a signal preventing operation of the door opening.

Abstract: An intrusion detector has a first sensor for monitoring a first condition and a second sensor for monitoring a second condition in a space to be protected against intrusion; a change in the condition sensed by the first sensor in a target area causes the second sensor to be aligned with the same target area; and if both sensors indicate a change in the respective conditions that they monitor an intrusion is indicated.

Abstract: A space surveillance apparatus includes at least one source of sonic radiation driven by a driver circuit as well as a processing or evaluation circuit. Upon movement of an object, or presence of a foreign object within a monitored space, the processing circuit triggers an alarm signal. Each sonic source defines the volume of its own monitored space, according to the equation:L=D.sup.2 /(4.lambda.),wherein:L=Length of main direction of radiation of the monitored space;D=Diameter of diaphragm of sonic source; and.lambda.=Wavelength of acoustic wave.The driver circuit drives the sonic source either in continuous mode, or in pulsed mode, and either at a constant wavelength or at a variable wavelength, i.e. in frequency modulation.

Abstract: A swimming pool alarm system is provided for actuating an alarm in response to the movement of a person in a swimming pool. The system includes a transmitter mounted below the surface of a swimming pool to continuously transmit ultrasonic sound waves through the body of water, and a similarly positioned receiver detects sound waves in the water and generates an electrical signal in response thereto. The electrical signal is continuously monitored, and the movement of a person in the pool alters the received ultrasonic sound waves and the corresponding electrical signal to produce an alarm signal for actuating an alarm indicator.

Abstract: A receptacle counting system includes an ultrasonic sound wave transducer for emitting ultrasonic sound waves and for receiving ultrasonic sound waves reflected from a receptacle whose contact level is to be sensed. There is a rim detector, responsive to the reflected ultrasonic sound waves, for determining the location of the rim of the receptacle and a receptacle detector, responsive to the rim detector, for indicating when a receptacle is present. One or more counters, responsive to the receptacle detector, are provided for monitoring the number of receptacles presented to the system.

Abstract: In an ultrasonic alarm installation, ultrasonic waves are continuously emitted into a monitored region and a frequency shift caused by a moving object, e.g. an intruder, is received by an ultrasonic receiver and evaluated by virtue of the Doppler effect for generating an alarm signal. For testing the ultrasonic alarm installation the emitted ultrasonic waves are modulated by a plurality of modulation frequencies in the range of the frequency shifts effective for triggering the alarm signal. Thus, the function test can be carried out using the same electrical evaluation circuit as for generating the alarm signal. The plurality of modulation frequencies conjointly with the switch-off of the transmitter signal has the effect that the reflected signals, which arrive at the ultrasonic receiver with different phase relationships, are not vectorially added to the ultrasonic transmitter signal to yield zero, so that a reliable function control is always ensured.

Abstract: A personnel detection and protection system comprises sensor means for detecting the presence of personnel in a prohibited operational zone, and for deriving signal means indicative of such a detected presence, and control means responsive to the deriving of such signal means to control the operation or movement of equipment in the prohibited zone.

Abstract: To accommodate for a change in the level of a received wave which occurs as a function of the distance between an object, the existence of which is to be detected, and a detector, the detector includes a receiver circuit which has an amplifier circuit having a gain which changes exponentially with an elapsed time since an ultrasonic wave has been transmitted. The amplifier circuit includes ramp signal generating means having an output level which changes in proportion to an elapsed time since a control signal assumes its on level, non-linear signal processing means for non-linearly processing a signal which is output from the ramp signal generating means, and a variable amplification amplifier having an amplification factor which depends on a signal level which is output from the non-linear signal processing means.

Abstract: A fluid-filled network of connected conduits and valves receives an acoustic signal in the form of waves of predetermined frequency, amplitude, and time sequence. At a second location, an acoustic receiver senses the form of the waves in frequency, amplitude, and time sequence arriving from the transmitter. The comparison between the acoustic signal introduced into the network and the signal received from the network represents whether the valve settings are satisfactory for using the network as a unit.

Abstract: Drift of the standing wave pattern in an acoustic doppler intrusion detection system in a confined space is compensated by adjusting the relative radiating and receiving positions of the radiator and receiver transducers, respectively, either mechanically or electrically until the signal level of the carrier wave at the receiver transducer is optimized. In the mechanical adjustment mode, either the receiver transducer or the radiating transducer is supported for movement relative to the other and is moved by a motor energized under the control of a signal level sensor circuit connected to the output of the receiver transducer. In another mode, a plurality of receiver (or alternatively radiator) transducers are connected through a switch to the signal level sensor circuit which in response to a drop in received signal level below a predetermined threshold, selectively switches the active transducer to optimize the received signal level.

Abstract: A bistatic sonar employing LMS adaptive spatial prediction is used to process against surface reverberation from the convergence zone (CZ). Hydrophones spatially separated from the primary array are used as references. The critical behavior exploited by the invention is that since the reverberation may be viewed as an extended source for the reverberation, the correlation drops off with separation between the reference and primary sensors, while it stays a constant for the plane wave target return. The reverberation is non-stationary, functionally dependent on the signal (even though the back scatter is statistically uncorrelated with the signal), and spatially extended over the sector of the CZ annulus cut out by the transmitter azimuth beamwidth. The detection of the target is based on the sudden appearance of one strong target point source within a densely packed region of weak point sources that have been constantly present and whose sum is much larger than the target.

Abstract: This invention is of an ultrasonic proximity switch having a range selection control circuit. The range selection control circuit is in this instance separated from the sensor by being installed in a separate housing which can be mounted in the switching unit. It is equipped with a potentiometer in the form of encoding switches and an actual value display which can be designed in the form of an LCD design. In addition, various selector switches can be mounted in the housing.

Abstract: An intrusion detector is configured to transmit signal(s) of a very short ration and then process the returned signal(s) reflected from various surfaces and objects within the propagation path in a room to be secured. The return signal(s) is a succession of peaks whose return times represent the location of respective objects. As configured, the intrusion detector apparatus includes, inter alia, a microprocessor that stores processed facsimiles of the return signal(s) for an unoccupied room and continually makes comparisons with subsequent returned signal(s). When the returned signal(s) changes, as a result of an unauthorized entry into the room, for example, a visual and/or audible alarm indication is produced.

Abstract: An obstacle sensing area ahead of a mobile robot is divided into a plurality of sensing regions. A number of ultrasonic transmitters and plural receivers on the robot cooperate to detect the presence of obstacles in the sensing regions. Coordinates representing four corners of each sensing region, and time data representing a time period from emission of ultrasonic waves from selected transmitters to reception of the waves by each receiver when the waves are reflected by an obstacle at each corner point, are prestored in data ROMs. The data ROMs are retrieved by a CPU in response to obtained time data, and precise position data of the obstacle in the sensing area is determined.

Abstract: A liquid discharge nozzle that dispenses liquid upon demand in a quantity that matches the volumetric capacity of the cup used to activate the nozzle. The nozzle has a first and second pair of diametrically opposed switch members that are disposed radially inwardly and outwardly, respectively, of an annular divider wall that depends to a bottom wall of the nozzle housing. The rim of a cup having a diameter less than the diameter of the divider wall engages the radially inwardly disposed switch members. The switch members, when so engaged or activated, make a call for service which results in the dispensing of the correct volume of liquid for that cup. The rim of a cup having a diameter greater than the diameter of the divider wall engages the radially outwardly positioned switch members which switch members when actuated cause liquid to be dispensed into the cup in the proper amount for that cup.

Abstract: A transmitting transducer is mounted on the outside wall of a vessel and supplies bursts of ultrasonic energy. If liquid is present, the energy is coupled to the other side of the vessel. Otherwise, the energy is attenuated. A receiving transducer (which may be the same as the transmitting transducer) is positioned to receive the ultrasonic energy if liquid is present. It is gated to be active only when such energy should arrive in the presence of liquid. The receiving transducer therefore generates an electrical signal indicating presence or absence of liquid in the vessel at the level at which the transducers are mounted.

Abstract: The presence of persons in a space is sensed with the aid of ultrasonic pulses which are sent out into the space when echoes of such ultrasonic pulses are received. Echoes attributable to the floor or to parts of a door in the space are timed out, and a remainder of such echoes is employed for sensing persons in the space. For example, sliding or revolving doors may be controlled and operated with the aid of such ultrasonic echoes, and limited access to secured areas may be provided thereby.

Abstract: A constant range ultrasonic motion detector features an ambient atmospheric condition sensor which senses the temperature, pressure, and percent relative humidity of the ambient atmosphere and produces therefrom a range compensation signal to adjust the sensitivity of the ultrasonic motion detector for stabilizing the range. The range compensation signal is applied to adapt detector amplifier gain and/or threshold level to the variation between design and ambient conditions. In one embodiment, an analog summing network at the ambient atmospheric sensor outputs provides the range compensation signal and in a second embodiment a microprocessor is operative to provide the range compensation signal.

Abstract: A control circuit (16) mounted on a faucet (10) operates an ultrasonic transducer (20) that transmits ultrasound into a target region (22) below the outlet (24) of the faucet. The control circuit receives electrical signals from the transducer when the transducer receives echoes from objects within the target region. The control circuit times the echoes to determine the distance of the object causing the echoes, and, if the distance of the object changes between successive measurements, the control circuit operates a valve (12) to permit water to flow. The circuit is powered by a rechargeable battery (18) that is charged by the action of a generator (31) that is driven by a turbine (34) powered by the flow of water through the faucet.

Abstract: The coded acoustic alarm transmitter/receiver system includes a transmitter for selectively providing both an audible alarm in the audio frequency range and a silent alarm in the ultrasonic frequency range. These alarm signals may be provided by a plurality of signals of different frequencies transmitted simultaneously in either the audio or ultrasonic frequency ranges. Receiver units are tuned to receive specific frequencies from a specific transmitter or group of transmitters.

Abstract: An intruder detector system employing Doppler radar consists of an encoder for modulating RF pulses with a cyclic pulse code, the code being cycled at a frequency equal to the RF pulse frequency and the pulses being modulated on a VHF carrier for transmission along one of a pair of parallel radiating cables. The signal received from the other cable is demodulated and digitized by a zero crossing detector functioning as a 1-bit analog-to-digital converter. A bank of exclusive-OR gates functioning as 1-bit correlators then simultaneously correlates each successive bit of the digitized signal with the values of the respective bits in each fixed position of the transmitted code sequence.

Abstract: A single transducer ultrasonic target detector and detection method are disclosed which provide for detection down to substantially zero distance from the detector housing envelope with an electroacoustic transducer subject to unavoidable ringing following emission of a burst of acoustic energy. The housing is configured with a retroreflecting surface proximate the transducer so that acoustic energy reflected from the target is repeatedly reflected back toward the target until the ringing has subsided sufficiently to permit reception of the reflected acoustic energy by the transducer.

Abstract: A motion detector system includes an ultrasonic transmitter, receiver and phase detector which produces as output signals of frequency related to the speed of movement of any moving object in a zone being monitored. The output of the phase detector is fed to two separate bandpass filters having different pass-bands characteristic of the frequencies generated by a human being moving in the zone being monitored. A warning is sounded only when signals have been present in both bands for more than a predetermined period.

Abstract: A novel visitor conversation system comprising a single transmitter-receiver. The distance to an incoming person is measured by receiving an ultrasonic wave signal propagated from the transmitter-receiver and reflected on the person. When the distance is shorter than a predetermined detection distance, it is decided that the person is a visitor. The transmitter-receiver further propagates an ultrasonic wave amplitude-modulated on an audio signal, and the signal received is demodulated for the purpose of a speech. The visitor detection and the conversation with a vehicle carrying a speaking device are performed by a single medium.