Abstract: A microwave frequency oscillator utilizing a push-push configuration to provide a low noise highly stable output signal at twice the frequency of a single resonator. The single resonator is connected in the feedback loop of two amplifiers. Additional circuit elements insure the proper oscillation conditions and relative phase are maintained. The use of a single resonator makes possible the application of various noise reduction techniques.

Abstract: A composite diode module is provided having an impedance matching member integrally formed within the module. The module includes a base member, a heat sink holder member having an aperture, a gold plated diamond heat sink which is disposed in the aforementioned aperture, and an encapsulant holder member having a second aperture. IMPATT diodes are disposed in dielectric spacers bonded to one end of the heat sink in alignment with the second aperture. A bias pin member is then bonded on the second end of the IMPATT and an encapsulant having selected electrical properties is provided in the second pair of apertures to secure the diode and to provide the diode module with a predetermined impedance characteristic. In a preferred embodiment, the module includes a pair of IMPATT diodes. With this arrangement, the module may be used in power combiners.

Abstract: A frequency-changeable microwave signal generator has a plurality of microwave signal oscillators, a plurality of branch lines connected to the microwave signal oscillators, a transmission line connected to the plurality of branch lines and provided with an output port at one end thereof, and a means for selectively operating one of the microwave signal oscillators. The line lengths of the branch lines are set such that the output impedance of the microwave signal oscillator connected thereto, which is measured from a branch point for connecting the transmission line and the branch line, is at maximum when the microwave signal oscillators are inoperative. The relation L=(.lambda./2)(k-1) (k is a natural number) is satisfied where L is a distance along the transmission line between adjacent branch portions of the branch lines connected to the transmission line, and .lambda. is a predetermined operational wavelength.

Abstract: The oscillator circuit comprises an amplifier having a pair of inputs, a positive feedback path producing a positive feedback ratio to one of the inputs, and a negative feedback path including a series resonant circuit producing a negative feedback ratio to the other of the inputs. The positive and negative feedback paths are independent such that the current in each of the paths can be adjusted independently. In this manner, a high Q multiplier effect is achieved. Also, the circuit has an output path which is separate from the input path so that a high output signal level can be achieved while maintaining a low current through the series resonant circuit.

Abstract: A high frequency oscillator is provided by connecting two amplifier circuits in parallel where each amplifier circuit provides the other amplifier circuit with the conditions necessary for oscillation. The inherent noise present in both amplifier circuits causes the quiescent current, and in turn, the generated frequency, to change. The changes in quiescent current cause the transconductance and the load impedance of each amplifier circuit to vary, and this in turn results in opposing changes in the input susceptance of each amplifier circuit. Because the changes in input susceptance oppose each other, the changes in quiescent current also oppose each other. The net result is that frequency stability is enhanced.

Abstract: An injection-locked waveguide oscillator comprises a first diode (3) having a free-running fundamental frequency above the local cut-off frequency of the waveguide (1) and a second diode (4) having a fundamental frequency below and a higher harmonic above the local cut-off frequency. The first diode (3) may be an IMPATT diode and the second diode (4) a Gunn diode. The free-running fundamental frequency of the first diode (3) is close to the higher harmonic of the second diode (4) so that the second diode (4) injection-locks the first (3). Locking in the reverse sense is inhibited by the inherent loss in conversion from the higher harmonic to the fundamental in the second diode (4), thus avoiding the need for a circulator or isolator. The two diodes (3, 4) preferably are mounted in a common waveguide (1) for a simple compact structure.

Abstract: A vital low frequency code generating circuit having a pair of complementary unijunction transistor relaxation oscillators for producing coincidental pulses in the absence of any failure; and a first initially nonconductive transistor amplifier and a second initially conductive transistor amplifier for saturating a square loop core transformer in a positive direction. The coincidental pulses causing the first transistor amplifier to be rendered nonconductive to unsaturate the square loop core transformer and causing the second transistor amplifier to be rendered conductive to saturate the square loop core transformer in the negative direction, which results in the development of output code pulses only when neither of the relaxation oscillators has drifted appreciably.

Abstract: A metallic support supports a number of semi-conductor devices surrounded by an annular dielectric substrate which in turn supports a circuit including at least two microstrip lines and a metallic circular output element. The small thickness and high dielectric constant of the substrate are selected to permit a reduction in width and in length of the microstrip lines which are folded-back in a curvelinear fashion and placed on the substrate along circular arcs which are concentric with the output element.

Abstract: Disclosed is equipment for testing a magnetic recording head; comprising a circuit which generates a test signal simulating what the head under test would generate.

Abstract: A solid state microwave power combiner is disclosed having a central combining cavity with a plurality of coaxial oscillator circuits disposed about and coupled to the cavity. The oscillator circuits are oriented such that their longitudinal axes are parallel with the central axis of the combining cavity. They alternate in configuration about the cavity such that adjacent oscillator circuits have their power generating diodes located on opposite sides of the cavity. In one embodiment, the coaxial lines used in the oscillator circuits have two parts of different sizes. The oscillator circuits are oriented about the cavity so that the smaller sized coaxial line part of one is adjacent the larger sized coaxial line part of the next. Both rectangular and circular combining cavities are disclosed.

Abstract: A power combiner circuit for combining a plurality of signals to provide output power to a load over a broad range of operating frequencies includes a resonant cavity and a plurality of negative resistance diodes which couple such signals into the resonant cavity. Each one of the negative resistance diodes is disposed in a corresponding one of a like plurality of coaxial oscillators. In a first embodiment of the invention, the end of the cavity coupled to the load includes a plurality of members which provide a plurality of resonant structures and which are used to reduce variations in the impedance of the cavity over the operating range of frequency. In a second embodiment of the invention, each one of the coaxial oscillators includes a plurality of ring members used to match the impedance of the diode to that of the cavity and to reduce variations in the impedance of the cavity over the operating range of frequency.

Abstract: A plurality of negative resistance devices is spaced below a cylindrical center conductor of a single coaxial cavity. Each negative resistance device has a bias device connected to it by a bias wire. Extending radially through the outer wall of the coaxial cavity is a coax cable with an RF coupling probe. A tuning screw is place axially through the interior of the center conductor for tuning the frequency of the power combiner.

Abstract: An oscillator circuit utilizing multiple (two) quartz crystal resonators as the frequency controlling elements in a novel circuit arrangement. The use of two crystal units increases the oscillator circuit signal transmission group delay by a factor of 2 to 3 and effects an estimated 6 dB reduction in oscillator output signal phase noise sideband level at carrier offset frequencies less than the resonator half-bandwidths. The degree of resonator tracking required is made practical with the use of temperature controlled SC-cut resonators. In addition, the oscillator circuit is configured so that equal, correlated output signal currents can be extracted from each resonator through individual load circuits, thereby increasing available oscillator output signal amplitude by 2:1 and reducing the net effect of uncorrelated load circuit additive noise by 3 dB.

Abstract: In a distributed IMPATT structure, power is coupled out through a side contact. That is, in previously proposed distributed IMPATT structures, the gain medium (the active region of the IMPATT) operates as a transmission line. The prior art has attempted to couple output power from the gain medium through an end contact, i.e., through a contact which is perpendicular to the primary direction of energy propagation (and also to the direction of maximum elongation) of the active medium. In the present invention, a sidewall contact extends in a direction which is parallel to the principal direction of propagation of the energy in the active medium. Thus, the sidewall contact plus the active region together can be considered as a single transmission line. This extended transmission line is also connected to a second distributed semiconductor element which functions as a varactor.

Abstract: The invention relates to an ultra-high frequency oscillator (11-14 GHz) having a plurality of transistors, stabilized on at least one of their electrodes by a microstrip line coupled to a dielectric resonator. The oscillator according to the invention groups the transistors on the periphery of an insulating substrate, which centrally supports a single dielectric resonator common to all the transistors. The microstrip lines have two end portions, which are not coupled and are parallel to the field lines of the resonator, and a coupled central portion, perpendicular to the field lines. The transistors and microstrip lines are coplanar. The output is by a coaxial cable at the center of the substrate or by a microstrip line coplanar to the substrate.

Abstract: A power oscillator for transmitter equipment operating at hyperfrequencies such as microwave links and radar. A plurality of elementary oscillators are coupled in parallel. Each elementary oscillator comprises a field effect transistor (FET) (11) connected in the common drain configuration with a first microstrip (51) connected to its gate and a second (21) connected to its source. Adjacent gates are interconnected by first resistances (R1) and adjacent sources by second resistances (R2). The resistances serve to balance the oscillators and to suppress parasitic oscillation. The free ends of the gate microstrips (21) are interconnected to synchronize the oscillators and the free ends of the source microstrips (51) are interconnected to constitute the oscillator outlet. The FETs may be disposed in a line or in a ring.

Abstract: A clock pulse regenerator uses a pair of oscillators each comprising a NOR gate and a transmission line feedback element. The oscillators are provided with complementary data pulses and provide an output signal only when the data signal is of a selected logic level. The output signals are combined to form a continuous regenerated clock signal. An FSK encoder using similar oscillators is also disclosed.

Abstract: A mm wavelength power combiner comprising an open resonator comprising a r of confronting concave reflectors which can be either spherical or parabolic. The resonator dimensions are many times the wavelength of the energy sources to be combined. A plurality of mm wave energy sources are applied to the resonator in such a way that the great majority of the energy bounces back and forth between the reflectors near the axis thereof in the fundamental or Gaussian mode. The design minimizes multimoding and diffraction losses.

Abstract: A distributed inductive reactance is coupled to a terminating impedance at the interface of a combiner probe with a resonant cavity. The distributed reactance is implemented by a metal insert having a cavity interface and having a coupling portion, which is coaxial with a cylindrical dielectric and with a cylindrical cavity in an end of the terminating impedance.

Abstract: A frequency memory module responsive to an input relatively short duration RF burst signal of center frequency f for producing an output signal at center frequency f for a relatively long duration includes a narrow band filter tuned to pass frequency f which is receptive of the input signal, an amplifier connected to the output of the filter and feedback means connected from the output of the amplifier to the input of the filter. Because of the feedback the frequency memory module sustains oscillations at frequency f long after the input pulse is removed from the filter.

Abstract: At least two oscillators (20) are power combined using planar transmission lines, e.g., microstrip, stripline, or suspended substrate. A portion (42) of each oscillator (20) is preferably implemented in suspended substrate while an impedance matching portion (24) is preferably implemented in microstrip. Each oscillator (20) comprises a two-terminal negative-resistance active device power source (22) such as a negative resistance diode. The sources (22) are all operated in phase in the even mode. Stabilizing resistors (8) connect adjacent oscillators (20) to keep the sources (22) in phase. A diplexer (29, 33) within each oscillator (20) isolates the RF output (and RF input when injection locking is employed) from the individual DC biases used for sources (22), controls out-of-band impedances, and isolates oscillators (20) from each other. The outputs of the oscillators (20) are summed at a common junction (12) via planar transmission line spokes (10) having equal lengths.

Abstract: An improved combiner of microwave power out of a plurality of coaxial diode oscillators is shown to be made up of a circular cylindrical cavity dimensioned to operate in the TM.sub.020 mode at a selected microwave frequency, with such oscillators being disposed about the periphery of both end planes of such cavity and each individual one of such oscillators being reentrant at an angle of 180.degree. so as to double the number of such oscillators as compared with the number of straight coaxial diode oscillators that may be disposed about the periphery of such cavity.

Abstract: A coherent array of Josephson oscillators is provided. Individual hysteresis-free Josephson junctions are longitudinally arranged in a line and have such a spacing as to substantially eliminate quasiparticle interactions. To provide a common frequency of operation, equal and opposite dc voltages are produced in adjacent pairs of the Josephson junctions by an arrangement of interlocking dc SQUID's (Superconductive Quantum Interference Device) connected to transversely extending biasing leads. Phase coherence for the array is provided by a rf current circulating in an inductive feedback path that loops between the ends of the array.

Abstract: A power combiner using a circularly cylindrical cavity, dimensioned to support the TM.sub.020 mode, to combine the power from coaxial diode oscillators is shown to comprise: (a) a first plurality of such oscillators disposed about the periphery of such cavity; (b) a second plurality of such oscillators disposed in coincidence with the first spatial null in the electric field in such cavity; and (c) a plurality, similar in number to the second plurality of such oscillators, of electrically conductive bridges interposed between the top and bottom walls of the cavity in-between the center conductors of the coaxial diode oscillators in the second plurlaity of such oscillators.

Abstract: A typical coaxial circuit which couples a negative resistance diode to the cavity of a power combiner consists of a metallic rod which is biased by a spring against the diode supported by a carrier which is effective to vary the position of the diode along the longitudinal axis of the rod. The rod cooperates with bores in a block to comprise, in series, between the diode and the cavity, a transmission line whose length varies in accordance with diode position, a fixed impedance transformer and a fixed length transmission line.

Abstract: A coherent array of Josephson oscillators is provided. Individual hysteresis-free Josephson junctions are longitudinally arranged in a gap of a central conductor in a line and have such a spacing as to substantially eliminate quasiparticle interactions. To provide a common frequency of operation, equal and opposite dc voltages are produced in adjacent pairs of the Josephson junctions by an arrangement of interlocking dc SQUID's (Superconductive Quantum Interference Device) connected to the longitudinal central conductor using microwave bias tees. Phase coherence for the array is provided by a rf current circulating in an inductive feedback path that loops between the ends of the array.

Abstract: A combiner for power combining electromagnetic energy is disclosed. At least two electromagnetic cavities are positioned having intercavity coupling among all cavities: each cavity is tangent to all other cavities and/or external transmission line connections are employed to enhance/provide intercavity coupling. Each cavity contains within it at least one power generating device. An input/output port is connected via a nonreciprocal device to an output load and an injecting oscillator which usually has a lower power level than that of the free-running combiner and a higher spectral purity. The cavities are intentionally tuned to at least two different frequencies. For the two cavity and three cavity embodiments, a greater bandwidth is obtained compared with prior art combiners where the cavities are tuned to the same frequency. The power loss is slight.

Abstract: The invention relates to a circuit arrangement for producing a low frequency alternating current, such as is particularly used for electric massaging. Any desired frequency characteristics and beats may be produced by the interconnecting of several generators having different, adjustable fundamental frequencies, and by an adjustability of the coupling components. These frequency characteristics and beats have proven to be particularly effective. Above all, the components of the line frequencies of 50-60 Hz, which are dangerous to the human body, are avoided.

Abstract: An efficient higher order mode resonant combiner in which a higher order mode accumulator cavity is adjusted to have the real part of its input characteristic impedance to be so minimized as to be less than the characteristic impedance Z.sub.o of the input circuit. When an active device is matched to this low, minimized value of cavity input impedance a mismatch results between the active device power source and the input to the combiner at undesired higher order modal frequencies. This resultant mismatch at undesired modal resonances obviates the need for mode suppression devices within the cavity which devices as taught in the prior art had detrimental effect of the efficiency of the combiner.

Abstract: A solid state microwave source placed within a rectangular waveguide, whose one end is short-circuited. The microwave source incorporates a negative resistance diode system placed on the inner wider wall of the waveguide and perpendicularly with respect to the waveguide transmission direction, a resonant microband line suspended by means of a dielectric substrate, a connecting means between the diode system and the resonant line, and means for connecting to an external polarization source.

Abstract: In a microstrip circuit having dual diode driven, independently oscillati half-wave open ring resonating sections, partially coupled quarter-wave ring sections are provided to permit matching and tuning of diodes having dissimilar negative impedances. The quarter wave ring sections are combined with appropriate line sections to accommodate the negative impedance devices. The diode circuits are connected to the low impedance points of the oscillating ring sections by the quarter-wave ring sections. Appropriate terminations to ground are provided to suppress possible oscillations in a bias circuit. Second and third harmonic traps are provided for use with TRAPATT diodes. Ground lines are provided to reduce circuit unbalance in the event of drastic power changes occuring on either side of the circuit which may other wise result in odd mode operation. Slots are provided to suppress an undesired transverse resonance mode in the line sections accommodating the negative impedance devices.

Abstract: A device for connecting plural oscillators to a single output port without he use of power dividers, switches or multiplexing filters. The plural oscillators produce multiple frequencies with only one oscillator operating at a given time. The oscillators are mounted in shunt waveguide cavities along a central waveguide manifold at distances from the central waveguide manifold and waveguide end so as not to affect the operating oscillator.

Abstract: A clock signal generator for providing redundant clock signals includes two clock modules that utilize phase-locked loop oscillators for generating clock and reference signals and for diagnosing malfunctions of the generated clock and reference signals. One clock module is selected as the master, and the other clock module is the slave, being phase and frequency locked to the master. Switching the master between the clock modules may be externally initiated by select signals and also is automatically initiated when malfunctions are detected. The master and slave clock modules are always phase and frequency locked to one another, even if both clock modules are malfunctioning. When both clock modules experience simultaneous malfunctions, the master is selected in accordance with the externally generated select signals. Since the master and slave clock modules are always phase and frequency locked, switching the master is transparent to clock signal utilization circuitry.

Abstract: There is disclosed herein a music synthesizer which responds to a music note played by a music instrument. The synthesizer has an envelope generator which generates a control signal in relation to the input signal to control the loudness of the synthesized note. Also, the synthesizer has a pair of voltage controlled oscillators, one of which provides a signal having a frequency related to the frequency of the input note, and the other of which provides a signal having a frequency related to the frequency of the input signal offset by the ratio of the difference between a programmed note and a referenced note, such as A440. The programmed note is that note following the operation of a control switch. The synthesizer further includes a series of footpads which control various functions of the synthesizer, such as programming the programmed note, to allow the user to control the synthesized sound while playing an instrument.

Abstract: A mechanical oscillator of the type which includes a mechanical resonator and a resonator driver connected in a regenerative signal loop in which the driver receives the resonant frequency signal of the resonator and provides, in response thereto, a constant magnitude drive signal of equal frequency and supporting phase to the resonator to maintain a minimum amplitude for the resonant frequency signal, is provided with dual resonator drivers actively connected in parallel in the regenerative loop, each providing through a load sharing network a proportionate amount of the total drive signal magnitude in complement with that provided by the other, and each providing the full drive signal magnitude in the presence of a failure of the other.

Abstract: An apparatus for combining outputs of serially connected high frequency power sources includes a number of input ports, an output port, and a power combination structure. The power combination structure includes two outer conductive layers which extend from the input ports to the output port and one or more intermediate conductive layers which extend from the input ports to a power combination region. High frequency power from the input ports propagates to the power combination region and therein combines vectorially. The sum of the individual input power levels then propagates to the output port. The power combiner can be reversed and used as a power divider operating into serially connected loads. A preferred embodiment, including two copper clad dielectric members and an aluminum base, operates at about 915 MHz. The power combiner can be constructed in a coaxial configuration.

Abstract: A microwave power combiner is shown to consist of a plurality of coaxial diode oscillators disposed on the periphery of a circularly cylindrical cavity operating in the TM.sub.020 mode, such cavity containing mode suppressor means to prevent any mode other than the TM.sub.020 from operating.

Abstract: The specification describes a solid state microwave power combiner wherein a plurality of solid state power generating devices are mounted between adjacent conical support and housing structures. These structures define the microwave electrical circuits for these devices, and also as provide a waveguiding region for propagating energy from these devices to a common output line. Both the support and housing structures have their apexes integrally joined, respectively, to input and output conductors of a common output coaxial line used for coupling power out of the combiner. This novel geometrical configuration minimizes the electrical distance between the power generating devices and the coaxial output line, maximizes the packing density of the structure and optimizes the electrical performance of RF termination elements for these devices.

Abstract: A microstrip circuit which features a pair of open ring resonators sections adapted to oscillate independently in their even mode. In a preferred form, the ring resonator sections are each driven by a TRAPATT diode, and include a load circuit which combines the individual power outputs to a common load. Tuning stubs and the like may be provided to reactively trap harmonics in order to initiate the desired TRAPATT mode, and additional ring resonators may be interposed between the driving circuit and the load to filter the fundamental frequency, if desired. Other configurations permit power to be combined from two or more sets of dual ring resonators.

Abstract: A driver circuit for a tone generator that is adapted to cause the tone generator to produce a pleasant sounding chime. The circuit comprises high and low frequency oscillator circuits whose decaying sawtooth type outputs are summed and modulated to produce the desired chime effect.

Abstract: A high peak power microwave generator is disclosed in which a plurality of transmission lines are connected to an output wave guide at predetermined intervals along the direction of propagation. Each transmission line is periodically charged, and this electromagnetic energy is released into the wave guide upon the actuation of a light activated silicon switch (LASS) diode connected to the transmission line. The LASS diodes are actuated simultaneously by a laser beam which traverses equal optical paths to each switch. The coincident switching of the transmission lines enables the power in each line to be additive in the wave guide, and much higher output pulses can be obtained. Further, the high speed switching capabilities afforded by the LASS diodes means that the resulting high power can be obtained at a much higher frequency.

Abstract: A modular microwave power combiner having a plurality of identical microwave diode amplifier circuits grouped in sets within the body of a modular unit which are electrically coupled in parallel to a central cavity sized to be resonant at a single frequency to minimize mismoding thereby enhancing combiner efficiency. A number of waveguides are provided for coupling of the microwave diode in each amplifier circuit to the resonant cavity, and the waveguides are situated on one side of a PC board at the top of each modular unit. Since each of the modular units is essentially identical in physical size and shape, the overall power output of the power combiner can be increased by merely adding additional modular units. The individual modular units are sized to fit top-to-bottom such that the respective resonant cavities are spaced apart by one-half wavelength (.lambda./2) for the parallel electrical coupling of all of the resonating cavities.

Abstract: An improved solid state transmitter (and elements therefor) adapted particularly well to pulsed operation at radio frequencies is disclosed. Such transmitter includes the combination of: A crystal-controlled oscillator producing a continuous wave output signal which, ultimately, determines the frequency of each transmitted pulse; a first oscillatory circuit, including a resonant cavity and at least one normally quiescent coaxial oscillator incorporating an IMPATT diode; a second oscillatory circuit, including a resonant cavity and a plurality of normally quiescent coaxial oscillators, each one of such oscillators incorporating an IMPATT diode; and an improved modulator for periodically actuating all of the IMPATT diodes in such a manner that a pulsed output of the first oscillatory circuit is produced which remains locked to the then existing continuous wave signal out of the crystal-controlled oscillator and the pulsed outputs of the coaxial oscillators in the second oscillatory circuit similarly are locked.

Abstract: In an oscillator or power combiner of the type operating at microwave, millimeter wave and above, apparatus for increasing the size, so that one or more active devices can be coupled to the oscillator, including a TM coaxial cavity operating at a predetermined frequency, which cavity has an output coupled thereto for removing power, and a second cavity operating at a dominant mode and coupled to the TM coaxial cavity, which second cavity assures efficient and spurious free operation of the oscillator or power combiner at the desired frequency.

Abstract: In a high power oscillator for frequencies on the order of microwave and above, a method and apparatus for tuning the oscillator in response to a control voltage applied thereto by utilizing a relatively low power varactor diode in a harmonic cavity coupled to the oscillator and without loss of efficiency.

Abstract: A microwave oscillator in which the power supplied by 2N microwave diodes such as avalanche or Gunn effect diodes is added. The diodes are connected together in two by sections of strip lines which enables magnetic coupling between these diodes and a dielectric resonator, with the diodes in each couple operating in phase opposition.

Abstract: A power combiner for solid state oscillator circuits is shown to be the combination of a central cavity and a plurality of subcavities, each one of the latter being dimensioned to operate in the TM.sub.010 mode to synchronize a plurality of solid state oscillator circuits. The central cavity and each one of the plurality of subcavities are coupled together through coaxial lines so that the central cavity in turn synchronizes the plurality of subcavities.

Abstract: In an oscillator of the type producing microwaves, millimeter waves and above, apparatus and a method for increasing the size, so that one or more active devices can be coupled to the oscillator, including a first cavity operating at a higher order mode, which cavity has an output coupled thereto for removing power, and a second cavity operating at a dominant mode and coupled to the first cavity, which second cavity assures efficient and spurious-free operation of the oscillator at the desired frequency.

Abstract: An improved solid state transmitter (and elements therefor) adapted particularly well to pulsed operation at radio frequencies is disclosed. Such transmitter includes the combination of: A crystal-controlled oscillator producing a continuous wave output signal which, ultimately, determines the frequency of each transmitted pulse; a first oscillatory circuit, including a resonant cavity and at least one normally quiescent coaxial oscillator incorporating an IMPATT diode; a second oscillatory circuit, including a resonant cavity and a plurality of normally quiescent coaxial oscillators, each one of such oscillators incorporating an IMPATT diode; and an improved modulator for periodically actuating all of the IMPATT diodes in such a manner that a pulsed output of the first oscillatory circuit is produced which remains locked to the then existing continuous wave signal out of the crystal-controlled oscillator and the pulsed outputs of the coaxial oscillators in the second oscillatory circuit similarly are locked.

Abstract: A fail-safe "OR" logic gate circuit which includes at least a first and a second level detector each of which has a voltage breakdown device and an oscillating circuit, a separate resonant tank circuit each of which is tuned to substantially the same frequency and being loosely coupled between each other, an amplifying circuit coupled to the output of each oscillating circuit, and a regulating-rectifying circuit coupled to the output of the amplifying circuit and producing a d.c. output signal when a d.c. input signal causes either or both of the voltage breakdown devices to break down and to exhibit a low impedance for causing the respective oscillating circuits to oscillate and supply a.c. signals to the amplifying circuit for rectification by the regulating-rectifying circuit.