Abstract: A bridge-type linear amplifier includes separate local feedback networks on each half-side channel of the amplifier and an additional feedback network between channels of the amplifier in order to correct for differences in current gains of output transistors and requisite drive currents.

Abstract: A multistage amplifier (1) consists of unit amplifiers (1a-1c) connected in series. A .lambda./2 strip line (20) is connected in parallel to the last stage unit amplifier (1c), so that a signal may bypass the last stage unit amplifier. When the last stage unit amplifier is disenabled, the signal bypasses the last stage unit amplifier, and the output power is reduced without a decrease of power efficiency in the other unit amplifiers. When all of the unit amplifiers are enabled and the strip line is grounded at the central point thereof, the output power is increased.

Abstract: An automatic gain control device for use in an optical memory device has a circuit for producing an amplification control signal which is fed back to a gain control amplifier through a sample-hold circuit. A pulse train detection circuit is provided for detecting the pulse train indicating that the data stored are a on the optical memory device is being playedback. When the pulse train is detected, the sample-hold circuit is made inactive so that the amplification control signal is directly fed back to the gain control amplifier, and when the pulse train ends, the sample-hold circuit is made active to hold the amplification control signal obtained at the end of the pulse train and to produce the amplification control signal held in the sample-hold circuit.

Abstract: A hierarchical current amplifier includes a first current mirror tier including a current mirror having an input coupled to an amplifier base terminal for receiving an input current, an output coupled to an amplifier collector terminal, and a pair of emitter terminals. A second current mirror tier includes two current mirrors corresponding to each emitter terminal in the first current mirror tier, each current mirror having an input coupled to one of the emitter terminals of the current mirror in the first current mirror tier. The two current outputs in the second tier are coupled to the amplifier collector terminal to provide current gain. Successive tiers of current mirrors may be added to provide more current gain.

Abstract: A branching filter for separating or combining two different frequencies without interference in radio communication equipment etc. One or both of two filter blocks for separating or combining two signal waves whose central frequency differ from each other are constructed from a dielectric bandpass filter which allows the desired wave of a block to pass and a SAW band stop filter being connected in series with said filter which allows the desired wave of a block to pass and stops passing of the desired wave of another block.

Abstract: An AC line filter in which a pair of windings are wound in an opposite dition to each other and are provided at opposing locations on a main core that forms a closed magnetic path. At least one auxiliary core which forms a shorter magnetic path than the main core is positioned adjacent the main core. The auxiliary core has at low frequency region an effective permeability higher than that of the main core. A portion of each of the pair of windings being provided in such a way that the portion is a concentrated winding which surrounds both the main core and the auxiliary core simultaneously.

Abstract: In order to obtain greater flexibility in the design of a linear-phase electrical filter comprising an acoustic surface wave device including a pair of apodized transducers intercoupled by means of a multi-strip coupler, for example to obtain more equal contributions by the two transducers to the gain versus frequency characteristic of the filter, the transducers are apodized differently but have mutually complementary non-linear phase characteristics. First a transfer characteristic corresponding to the collective contribution to the desired overall gain versus frequency characteristic of the filter, is derived in terms of the z-transform and the roots or the reciprocals of the roots of the resulting polynomial in z.sup.-1 are found. These roots or reciprocals are then divided into two groups so that at least one pair of non-identical roots or reciprocals which have equal ratios between their real and imaginary parts and the product of the moduli of which is equal to unity are included one in each group.

Abstract: A relay comprises a yoke, an armature, a movable contact spring having a movable contact, at least one stationary contact mounted thereon, and a core. An air damper is mounted on a free end of the movable spring, or on a free end of the armature, to reduce sound generated by the impulsive force of the movable contact and the impulsive force of the armature.

Abstract: A breaking device for a low voltage circuit breaker comprises in each pole a switching bar, a pair of stationary contacts connected to the connection terminals, a double-break rotary contact extending in a housing of the bar, and two arc chutes disposed on each side of the bar. Two contact pressure springs ensure elastic positioning of the rotary contact along the longitudinal direction of the pole. Pivoting of the rotary contact takes place around a fictitious axis mounted floating with respect to the fixed rotation axis of the bar.

Abstract: An electromagnetic drive actuator including a magnetic circuit comprising at least one yoke having plate-shaped, L-shaped, E-shaped cross section or the like, at least one magnet mounted on the yoke and a magnetic flux extending from the magnet to the yoke, at least one coil arranged so as to cross the magnetic flux and produce a drive force in a direction crossing a plane including the magnetic path of the magnetic circuit when current is applied to the coil, and at least one magnetic shield member provided at the side portion of the coil to thereby prevent a counter drive force from being produced in a direction opposite to a desired direction of a drive force produced by the coil.

Abstract: Bistable magnet, in particular for the actuation of valves and the like, with a movable piston that has a pole face and that is held by a permanent magnet in one of its two stable positions, wherein this piston has a stop face that is provided with a damping plate and that with an opposing face that is built stationary into the housing defines an end position of the piston. To avoid switching noises without decreasing the holding forces it is provided that, in addition to the stop face on the piston, a pole face is provided that interacts with a stationary pole face and that a device that guides the magnetic flux and bridges the air gap between these pole faces is provided between these pole faces.

Abstract: A rotary variable differential transformer produces a substantially linear output over about 180 degrees of rotation of a rotor core. The transformer includes a base housing having a central bore, and a rotor having a shaft whose angular displacement is to be determined and a generally planar, circular rotor core mounted off-center at one end of the shaft and in a plane normal thereto. The rotor core is rotatably disposed within the opening of the base housing. Also included is a primary coil disposed in the opening of the base housing to circumscribe the shaft at a location rearwardly of the rotor core. First and second windings, with cores, are carried by the base housing and positioned about the base housing opening so that the axes of the coils are oriented radially of the opening and generally in a common plane with the rotor core. The first and second windings are connected together in series opposition.

Abstract: A fail-safe secondary fuse device for assuring the grounding of a conductive gas tube used in modular protection devices for individual subscriber circuit pairs. The device resiliently engages each of the three end and center electrodes normally provided on the tube. In the case of the end electrodes, the device is insulated from direct electrical communication by a fusible sleeve of insulative material which fuses under heat emanating from the gas tube with the occurrence of continued current overload.

Abstract: An electric fuse of the type which has a tubular fuse casing and a solid fuse end terminal telescopically received within the fuse casing is provided with an annular seal which is contained within an annular groove formed in the outer lateral wall of the end terminal. The seal is formed from a settable material which has been injected into the groove through a seal injection opening in the outer end of the end terminal which extends from the axial outer end and into fluid communication with an annular groove provided in the end terminal. A seal material bleed opening is provided in the end terminal which also extends from the axial outer end of the end terminal and into fluid communication with the annular groove. The bleed opening is positioned substantially diametrically opposed to the seal injection opening.

Abstract: An electrical apparatus is provided for use with a potentiometer or variable resistance element which does not require a mechanical connection between a contact member and an activating mechanism. This is accomplished by using a magnet in at least a portion of either the contact member or the activating mechanism while constructing at least a portion of the other of such contact member and the activating mechanism of a ferromagnetic material.

Abstract: An electric laminar resistor and the method of making same wherein a thin metal film is applied to a ceramic substrate. Metal film material is removed to form a resistance track and recessed connecting zones at opposite ends of the track. A burnt-in thick layer paste is extended through the connecting zone recesses and solidified to form connecting elements that are adhered to the substrate. A glass frit coating is applied over the resistance track, but not over the connecting elements. The resistance of the resistor may be adjusted by separating a part of the track.

Abstract: A vehicle security system can be fitted to a vehicle which has a radio transmitting device such as a cellular telephone, PMR or CB set. A control unit is arranged to periodically alert the driver of the vehicle to record a location message. When an alarm condition is signalled to the control unit from an alarm system, a panic button or a ratio receiver co-operable with a remote panic button transmitter, the control unit initiates a transmission from the radio transmitting device. The message transmitted includes the last recorded location message and may also include vehicle identification information and a mileage update message generated in response to the output of a vehicle odometer to indicate the distance travelled by the vehicle since the last location message was recorded by the driver. The same security system may also be constructed as a portable unit.

Abstract: An automotive vehicle control system is equipped with a main electronic control unit for controlling devices mounted on the vehicle, and an emergency electronic control unit for backing up the main electronic control unit. Both electronic control units transmit diagnostic signals, receive the diagnostic signals from each other and diagnose them for abnormalities, whereby a fault in the main electronic control unit is diagnosed by the emergency electronic control unit and a fault in the emergency electronic control unit is diagnosed by the main electronic control unit.

Abstract: A dipstick with automatic warning device consisting of a tube positioned in a dipstick housing of an oil pan, indicia disposed on the tube indicating ADD and FILL of the oil pan, sets of elecrical contacts disposed internally of the tube, one set proximate the ADD indicia and one set proximate the FULL indicia. A plastic cap located below the ADD indicia and having a bore therethrough for passage of oil from the oil pan cap internal of lower end of the tube. A conductive float ball within the tube to bridge respective sets of electrical contacts.

Abstract: A flasher device flashes a selected one of a plurality of groups of indicator lamps selected by a flasher starting switch. An intermittent voltage is supplied to the selected group of indicator lamps to cause the lamps to flash. A capacitor is operatively connected to the selected group of indicator lamps and the rate of change of the voltage across the capacitor is indicative of the resistance of the selected group of indicator lamps. The frequency of the intermittent voltage supplied to the indicator lamps to flash the lamps is varied in response to the rate of change of the voltage across the capacitor. As the rate of change of voltage across the capacitor varies in relationship to the resistance of the selected group of indicator lamps, the change in the frequency of the intermittent voltage supplied the indicator lamps and thus the flash rate of the indicator lamps is representative of the resistance of the group of lamps.

Abstract: An alarm device is disclosed to indicate the opening of an access element of a containment chamber carrying dangerous materials, such as a drawer or cupboard door, by children or similar intellectually unsophisticated persons. The alarm device provides two switches that are sequentially activated by a pivotally movable, externally projecting, wedge shaped sensor that moves outwardly to cause alarm annunciation at, or at a predetermined time after activation, if not deactivated by further outward manual motion before or after alarm annunciation. The alarm device is battery powered and operated by solid state electronic circuitry that is contained in a small compact casement that serves as a mounting means.

Abstract: An infrared light emitter forms a beam of infrared (IR) light directed onto a set of mirrors or reflecting surfaces arranged to form a closed path about a swimming pool and spaced above the pool deck a sufficient amount so as to be intercepted by anyone who might walk through it. After the reflected beam has traversed the closed path about the pool, it then impinges upon a light detector. An electric circuit provides a continuous alarm which can either be sound or visual upon beam interruption and which must be manually reset before it becomes inactive. The monitoring system may be actuated so the operative state by a handheld radio frequency transmitter. Electrical power for the system can be a rechargeable battery which is recharged by a solar array mounted directly onto a part of the system obviating the need for interconnecting cable wiring.

Abstract: This invention relates to a deactivatable tag useable with an electronic article surveillance system and comprised of planar conductive material cut into a pair of inverse, first and second spiral conductors wrapped about each other and positioned for capacitive and inductive coupling. The invention also relates to method of making tags wherein conductors are cut from a planar web of conductive material in a continuous process in a manner that the cutting results in the formation of two spiral conductors without accompanying waste of conductive material, and thereafter positioning the conductors to provide resonant circuits. The conductors of each pair are connected by welding to provide a reliable circuit. A film of electrostatic-charge-draining material on a web of deactivatable tags prevents their premature deactivation.

Abstract: Livestock entering a border zone along a vehicle roadway are deterred by devices triggered into operation simultaneously with a remote alarm by interruption of photo-electric beams at ends of the zone from which the animals enter or exit. The deterring apparatus is reset to prevent operation in response to travel of a vehicle through the zone and is temporarily disabled by selective switch actuation.

Abstract: An alarm system for warning of a creosote chimney fire hazard, having both means to produce a visible alarm when the creosote temperature is nearing the creosote flash point, and means to produce an audible alarm when light from actual ignition of a creosote fire is detected. The invention also provides means to discriminate against detection of wood fire light, to minimize false alarms.

Abstract: A device for detecting the unbalance of a rotating machine from a predetermined threshold. This device includes a pendulum formed from a vertical rod made of an elastically deformable metal, the upper end of which is embedded in an insulating support fixed rigidly to the housing of the rotating machine and which at its lower end carries a metallic mass, the mass being received concentrically, with a predetermined peripheral play, within a metal rink likewise fixed to the housing and insulated electrically from the housing, the ring and the embedded end of the pendulum being connected electrically to an electrical alarm or safety circuit which closes as soon as the mass comes in contact with the ring, where the resonance frequency of the pendulum is below that of the parts of the rotating machine which is subjected to the unbalanced condition.

Abstract: An input device for providing X and Y coordinate analog input values and an associated function selection to a computer. There is a support plate and a multiposition function selection switch having an output indicating the position thereof. There is also selector apparatus carried by the support plate and operably connected for moving the function selection switch between its positions. There are coordinate generators for generating X and Y coordinate analog values at outputs thereof and activator apparatus carried in combination with the selector apparatus and operably connected to the coordinate generators for changing the X and Y analog values being output. The selector apparatus may comprise an annular member disposed parallel to the plane of the support plate with the activator apparatus disposed within the annular member. The function selection switch is a rotatable switch and the annular member is rotatable about a perpendicular axis to move the function selection switch between its positions.

Abstract: A touch controlled display device has, in one embodiment, two displaying segments disposed on the inside of a front cover window in an LCD unit. Further to causing the segments to display different sign information by providing them with different feeds, they are both utilized as sensing means included in a capacitative sensing circuit which is activable by the finger of an operator.

Abstract: A graphics display apparatus with a combined bit buffer and character graphics store includes a coded display buffer containing pointers to the store. The store is constituted by odd and even memories used to derive bit patterns for odd and even character cell columns on the display and is partitioned into a font area and a bit buffer area. In a first mode of operation, compatible with existing programmed symbol arrangements, pointers in the coded display buffer in conjunction with odd/even select signals and slice signals derive the bit patterns for each raster scan line of the display. In a second mode of operation, a graphic image to be displayed is stored as a bit map in the bit buffer area: the required bit pattern is derived using slice and odd/even select signals in conjunction with pointers stored in the coded display buffer.

Abstract: A data communication apparatus comprises means for registering a destination station identification code number, means for storing information, and control means for setting a communication mode by the destination station identification code registration means and the information storing means.

Abstract: In an interface module for connecting user terminals of the carrier sense multiple access collision detection (CSMA/CD) local area network (LAN) to a different access mode switching network, a transmit buffer is connected at one end through a transmit data channel to a user terminal and connected at the other end to a desired swtching system. A receive buffer is connected at one end to the switching system to store a receive packet supplied from it. An OR gate is provided having a first input connected to the transmit data channel, a second input connected to the other end of the receive buffer and an output connected through a receive data channel to the user terminal. A detector circuit detects when a transmit packet is received from the user terminal.

Abstract: A matrix logic circuit network comprises a great number of interconnected logic gates. Input and output lines of the logic gates are arranged in the matrix array. By rearranging the input and output lines of the matrix in accordance with a sort algorithm, direct connection points of the input and output lines to which the same signals are allotted and connecting elements forming logic gates located at given intersections of the input and output lines are arranged within a diagonal area with a limited width, which extends along a diagonal line of the matrix.

Abstract: A digital television chassis and a picture-in-picture module are interconnected with control microprocessor means via a three wire communications bus. Function control units in the digital chassis and in the picture-in-picture module have identical digital addresses. A logic circuit is interposed in the Ident line from the microprocessor and the Ident lines to each of the digital chassis and PIP module for selectively controlling the digital chassis and the PIP module. The microprocessor addresses the logic circuit and provides a Data signal indicating which of the digital chassis and PIP module is to be controlled.

Abstract: A communication receiver is disclosed which can decode signals transmitted by radio frequency propagation. A programmable controller uses instructions in a non-volatile reprogrammable memory to decode and process the signals, and to output the information contained in the signals in a useable form. The controller also responds to predetermined signals by decoding and processing information for new decoding and operating instructions, and stores the data in a temporary memory. Logic circuitry responds to subsequent predetermined signals to enable selective reprogramming of the non-volatile reprogrammable memory by data stored in the temporary memory to alter the decoding characteristics of the receiver.

Abstract: In a radio paging system, radio paging signals contain a BCH (31, 16) format address and a BCH (31, 21) format address which are sent from a central station. The paper is assigned first and second BCH format user identification codes corresponding respectively to the BCH (31, 16) and BCH (31, 21) addresses. The pager has mode select switches for selecting the BCH (31, 16) address for local area reception or BCH (31, 21) address for wide area reception. When a paging signal is received, a coincidence is detected between the selected address and the corresponding BCH user identification code. When the coincidence is detected, the user is alerted to the reception by a paging signal. An appropriate channel is established in the local or wide service area.

Abstract: A monitoring apparatus for a safety device for driving a vehicle in reverse comprising at least two transmitter/receiver pairs which are mounted at the back of the vehicle and which operate by reflecting sound. Each transmitter/receiver is associated with an electroacoustic transducer. An acoustic shunt is positioned between neighboring transducers. The transmitter/receiver pairs alternate cyclically to acquire an object. The signal received from a neighboring transmitter is evaluated as a function control signal.

Abstract: A pitch limit symbol is generated at an aircraft attitude indicator which provides a pilot with display of a stall warning angle of attack margin which is referenced to an airplane symbol on the primary attitude indicator. The position of the pitch limit symbol relative to the aircraft symbol is a function of the difference in angle of attack between the current angle of attack at the aircraft, and a predetermined angle of attack at which the onset of stall warning occurs. Additional information is provided on the attitude indicator by a flight path angle symbol. The pitch limit symbol together with the flight path angle symbol provides the pilot with information to achieve a positive rate of climb during a pitch up maneuver while adjusting the pitch attitude of the aircraft to avoid a stall situation. The position of the pitch limit symbol may be compensated by various means to decrease the distance between the aircraft symbol and the pitch limit symbol.This is a continuation of application Ser. No.

Abstract: A single-step digital-to-analog converter includes a multiplicity of individual interconnected sources disposed in a matrix having matrix rows and matrix columns; a decoder apparatus connected to the matrix for addressing the individual sources, the decoder apparatus including a column decoder for addressing at least the more significant part of an n-bit-wide digital word to be converted and a row decoder in the form of a thermometer decoder.Logic apparatus is connected between the decoder apparatus and the matrix for determining the matrix column of one of the individual sources being addressed and for suppressing switching over of the individual sources of others of the columns. The logic apparatus includes first and second logic devices, the first logic device being connected between the column decoder and the matrix for deriving further column information (E.sub.i) and additional information (S.sub.i) from column information (X.sub.i) in accordance with the logical equations: E.sub.i =S.sub.i and S.sub.

Abstract: A digital signal processing circuit for processing input analog signals such as audio signals and video signals in the form of digital signals comprises an analog-to-digital converter for converting an input analog signal to a digital signal, a digital signal processing section for subjecting an output digital signal of the analog-to-digital converter to a digital signal processing including a processing for digitally amplifying the signal, a digital-to-analog converter for converting an output signal of the digital processing section to an analog signal, and an attenuator provided on the input side of the digital signal processing section for attenuating the digital signal provided by the analog-to-digital converter to a value which is below a value at which the digital signal processing section overflows.

Abstract: A dual-slope A/D converter circuit has an oscillator (14) whose timing frequency is determined by the value of an oscillator resistor (70) and a oscillator capacitor (72). An integrator (66) integrates an input voltage at a rate determined by an integrating resistor (64) and an integrating capacitor (68). The oscillator resistor (70) and integrator resistor (64) are designed such that their ratio will remain constant despite variations in actual value due to manufacturing inaccuracies. The oscillator capacitor (72) and integrating capacitor (68) are similarly designed. Consequently, an optimum peak integration value can be obtained at full scale input despite variations in actual resistive and capacitive values.

Abstract: A digital modulation signal is sampled by an A/D converter in a predetermined cycle. A phase interval P between a zero level crossing and the current sampling point using sampling data S.sub.i+1 at the current sampling point and sampling data S.sub.i at a sampling point which is located one point before the current sampling point. A phase P.sub.i+1 of the current sampling point is found using the phase interval P, a phase P.sub.i of the sampling point which is located one point before the current sampling point, a phase P.sub.i -1 of a sampling point which is located two points before the current sampling point and a phase P.sub.i-2 of a sampling point which is located three points before the current sampling point. A clock signal is detected using the phases P.sub.i+1 and P.sub.i. Digital data is detected using the phase interval P, the phase P.sub.i+1 and the sampling data S.sub.i at the sampling point which is located one point before the current sampling point.

Abstract: A high speed comparator unit for a flash A/D converter in which a bank of comparator units compare simultaneously an analog input voltage with equally spaced reference voltages, and an encoder ROM produces digital signals based on the comparator unit's outputs. The comparator unit includes a two-stage cascode configuration and a level shifter configuration which effectively reduces the miller-effect of the comparator unit.

Abstract: To obtain better accuracy, it is known to modify the mechanical metered volume reading of the flow through a gas pipeline according to the gas laws, which incorporate the pressure and temperature parameters of the gas. The present invention samples those parameters with analog sensors and inputs them into an analog to digital converter. The digital output from the converter is employed to obtain a more accurate digital volume reading.

Abstract: A synthetic aperture radar processing system receiving return data from a plurality of transmitted pulses which utilizes frequency alignment for partitioning the received data into patches of data in an orderly sequence, a plurality of patches of data being formed in each of a plurality of range subswaths and being sequentially aligned in range columns. For each subswath, the return data is filtered in patch filters having wide bandwidths and passband overlaps selected so that each patch of data is totally included within a passband. The patch filters are selected for each subswath to provide sequential columns of data. Each patch of data for each subswath is then frequency shifted to an interpolator narrow band filter having a passband selected so that data outside of each patch is eliminated.

Abstract: Diclosed is a dual band communication receiver for use in a burst communication sytem. The receiver is capable of esentially simultaneous reception at a first carrier frequency (L), such as L-band and a higher carrier frequency (H), such as S-band, using distinct codes and replying in the frequency band received. A typical system is composed of a transponder and an interrogator. The incoming coded signal is down converted to an i.f. frequency compatible with surface acoustic wave (SAW) convolvers. The i.f. signal is then divided between two SAW convolvers, each having a convolution interval of two times the message symbol length (2T). Reference signals A and B are composite signals comprised of alternate L-band and H-band signals, each having a time period equal to T and each L- or H-band signal operating at a 50% duty cycle. Reference signals A and B are time reversed to the input signals applied to the convolver and are orthogonal to one another.

Abstract: An electromagnetic test method simulates the effects of plane electromagnetic wave illumination on a conducting body. A conductive sheet is placed in the vicinity of the body and connected to an electrical ground. Alternating current from a current generator is injected into the conducting body via electrodes positioned at spatially separated points on the body's surface. The fields generated by the injected currents and the mirror currents in the grounded conducting sheet induce fields which create an overall current distribution in the conducting body substantially identical with that resulting from the incidence of a plane electromagnetic wave upon the body.

Abstract: A millimeter wave sensing device is disclosed comprising a local oscillator source generating a millimeter wave signal which is mixed with millimeter wave radiation reflected from or emitted by objects in a field of view. The mixing is performed in a staring array of mixer/detector elements which need not be mechanically or electronically scanned to generate signals responsive to the entire field of view. In a first embodiment of the invention, the device detects millimeter wave radiation emitted by or reflected from the object to be imaged. In a second embodiment of the invention, the oscillator used to provide the local oscillator signal is also used to illuminate the field of view. In the second embodiment of the invention, the oscillator signal is preferably linearly polarized, and a polarizing grid is used to separate the local oscillator signal and illumination beam and direct them in a simple and efficient manner.

Abstract: Measurement of flux density at the edges of the footprint of an RF transmission from a spacecraft with a view to determining the spacecraft antenna pointing error is difficult because of atmospheric fading local to the measuring station. Previous proposals to permit determination of pointing error in the face of such effects involve additional hardware on board the craft. Herein, it is proposed to induce a relatively small repetitive scanning motion of the spacecraft hence producing an oscillatory flux density variation at peripheral ground stations and then measuring the oscillatory component relative to the average flux density--frequency analysis equipment operable to discriminate the known frequency of the variation over a plurality of wavelengths can be used giving substantial accuracy improvement. A series of measurements enable the diurnal pointing error pattern to be determined and hence a spacecraft attitude correction command program to be produced.

Abstract: There is disclosed a system and technique for providing an audio verification of Global Positioning System (GPS) receiver signal acquisition. In a GPS receiver, the correlated output of the GPS signal is generally represented as a data modified CW signal with a Doppler component caused by the movement of a GPS satellite with respect to the receiver. Due to the Doppler component, this signal output provides a signature which is indicative of the particular satellite from which the signal is being received. The signal output is mixed with a local oscillator to produce a beat frequency in the audio band which may be filtered and coupled to an audio amplifier to produce an audio tone. The presence of the audio tone indicates the acquisition of a selected satellite signal and its audio frequency is indicative of the particular satellite signal being received.

Abstract: An airborne surveillance method and system allows an observer aircraft to determine the position and change of position of a multiplicity of target aircraft and thus allows analysis of collision threats from these aircraft. The system uses a phase comparison direction finding antenna to determine direction of nearby ground based SSRs and all target aircraft of interest. The system further makes use of all other available data including Mode C transponder generated altitude information of the target aircraft, the altitude of the observer aircraft, the received signal strength of both the SSR beam and the received transponder signal, the time difference of arrival between the SSR interrogation signal and the response from the target aircraft, and a variety of other factors to determine the position of the target aircraft.