Abstract: Monitoring of trigger circuits of power switches of electrical power supply devices which can experience faults due to breakage of conductors, oxidation of contacts, loosened terminal contacts, short circuits in trigger coils, etc. In order to improve fault monitoring, oscillator oscillations are applied to the trigger circuit of a power switch and are monitored. A fault- or alarm signal is generated in response to a detuning of an oscillator when the detuning persists for a predetermined time. The inductance of the circuit-breaking coil of the power switch serves as a frequency-determining element of the oscillator. A lag element with a delay of 500 ms is inserted after the oscillator. If the oscillator stays detuned for more than 500 ms, a Schmitt trigger is triggered by the lag element, whereby an alarm relay is actuated which switches on an alarm device via an alarm relay contact.

Abstract: In a vehicle detection apparatus having a plurality of channels, each arranged for detecting vehicles according to their influence upon the frequency of a respective loop oscillator the oscillation frequency of which is dependent on the inductance of a respective vehicle-sensing inductive loop, a common computer performs a calculation for each channel in turn whereby changes in the frequency of the respective loop oscillator are monitored and analysed. In one embodiment, the computer calculates an appropriate operational number, the time taken for that particular number of loop cycles to occur is measured and stored as a period count and the period count is compared with an environmental reference number to determine whether or not a vehicle detected flag should be raised or lowered. Neither the operational number calculated by the computer nor the reference number is fixed but provision is made for updating both.

Abstract: A disciplined oscillator system having a standard oscillator which is automatically corrected for both frequency errors and time error accumulation to a constant frequency signal which is derived from the WWVB carrier frequency and the WWVB TIME CODE to maintain overall frequency accuracy within one part in 10.sup.9 notwithstanding oscillator aging and in spite of jitter and distortion due to propagation delays and noise which may cause loss of, or time jitter in, the WWVB signals. Frequency errors are detected through the use of a counter (24) having a measurement accuracy greater than one part in 10.sup.10. An error detector (26) derives correction signals by averaging a plurality of frequency variances obtained in successive measurement cycles.

Abstract: An alarm circuit operatively associated with a phase-locked loop provides an error indication when the phases of the referenced signal and voltage controlled oscillator signal lose synchronization for times less than one millisecond. The alarm circuit includes an amplifier connected to receive the phase detector error signal, and an impedance connected to conduct the phase detector error signal to the amplifier. The impedance and amplifier have a frequency response corresponding to a frequency response of an associated receiver circuit, so that short duration deviations in the reference signal frequency which the receiver circuit cannot track produce an error indication and long duration deviations which can be tracked by the receiver circuit do not produce an error indication.

Abstract: A touch control arrangement which employs a touch panel comprising a plurality of touch keys and a network of electrically connected capacitive elements; an oscillator which incorporates the network of capacitive elements in its timing circuit; and a microprocessor coupled to the output of the oscillator and operative to control various appliance operating components as determined by the frequency of the oscillator output signal. The keys of the touch panel are operatively coupled to the network of capacitive elements such that actuation of a key or pad by the user changes the equivalent capacitance of the timing circuit causing the oscillator a generate a control signal at the frequency associated with the actuated key.

Abstract: A scan rate switch is interfaced to a microprocessor which controls a digitally programmed frequency synthesizer. The scan rate switch includes a plurality of different increment or decrement (frequency steps) positions with the apparatus changing the frequency at a fixed rate of five steps per second for as long as the switch is in any of the positions.

Abstract: The present invention relates to the design and fabrication of a probe, ancillary signal conditioning circuits with display circuits and related equipment required to measure the resonate frequency and display the shape of the resonance curve. The probe uses the energy absorbing method of indicating these parameters. A graphical display or an analog meter dip indicates the resonant frequency. A digital frequency meter can measures the frequency points precisely.

Abstract: A garage door opener system includes a radio receiver actuable by reception of a preselected radio signal for moving a garage door between opened and closed positions and a portable hand-held transmitter manually actuable to transmit such preselected radio signal to the receiver. The transmitter includes a radio frequency oscillator for producing the radio signal to be transmitted and a modulating means manually actuable to cause the oscillator to transmit a radio signal which is of the preselected form. An audio transducer is connected in parallel with the radio frequency oscillator to the output of the modulating means to produce an audio signal which corresponds in form to the electric signal modulating the radio frequency oscillator, which audio signal is audible to a person holding the portable transmitter.

Abstract: A tire pressure monitoring system includes a tuned circuit with a pressure sensitive switch which is closed when the tire pressure is normal, connected across it, the tuned circuit and switch being mounted on the vehicle wheel. Mounted on a part of the vehicle is a detector circuit including an oscillator which includes an inductor which is at least intermittently coupled to the inductor of the tuned circuit. When the switch is closed the oscillator runs normally and its output is detected to indicate that all is well. When switch is open, however, the oscillator output is suppressed whenever the inductors are coupled together. The circuit can also be used in other applications where it is required to detect the state of an isolated switch.

Abstract: An RF generator monitor circuit is provided for checking for variation in frequency of an RF generator outside predetermined limits. The circuit includes means for sampling the output of an RF generator, means for clamping the sample signal to prevent damage to the circuit from an exceptionally strong signal, means for converting the clamped sample signal to a positive going square wave, and for amplifying the square wave. Also included is a phase locked loop integrated circuit having the amplified square wave as an input. The phase locked loop integrated circuit includes a linear voltage-controlled oscillator and two different phase comparators. The input square wave signal is compared to the voltage controlled oscillator and an error voltage proportion to phase differences is produced. The error voltage is used as a control for the voltage controlled oscillator.

Abstract: An oscillation system, having a vibrator, a resonant bridge and a low resistance, oscillates at desirable frequencies by receiving an excitation signal amplified to a predetermined value by an amplifier. A detection feedback signal containing the resonant frequency of the vibrator is input to a phase shift circuit. The phase shift circuit adjusts the phase of the detection feedback signal and the excitation signal to satisfy the oscillation condition. The output signal from the phase shift circuit is input to a PLL comprised of a phase comparator, a low pass filter, an amplifier and a voltage controlled oscillator. The frequency of the output signal from the PLL follows the resonant frequency of the vibrator and is locked. Its output signal is applied to the amplifier which feeds the oscillation system. An analog multiplier circuit is fed with signals proportional to the current and voltage from the resonant bridge circuit, and outputs the product of these signals.

Abstract: A channel indicator suitable for use in a television receiver and an FM receiver each having an electronic tuner is disclosed in which a channel number now being received can be automatically indicated by counting the number of those local oscillation frequencies corresponding to respective channels which the local oscillation frequency of the electronic tuner has passed prior at the arrival to a desired value. Means for compensating for irregular frequency channel intervals and temperature variations are included.

Abstract: A display in a superheterodyne receiver having a local oscillator, adapted for displaying in a digital manner the frequency of a signal being received by the receiver by counting the local oscillation frequency by means of a preset counter wherein the data for the prescribed intermediate frequency or the complement thereof is preset. A reference voltage is generated by means of a variable resistor for correcting the difference between the preset value for the prescribed intermediate frequency and the actual intermediate frequency of the intermediate frequency stage of a receiver as actually manufactured, and a comparison voltage is obtained by digital/analog converting the output of a multiple-bit counter which is stepped responsive to clock pulses.

Abstract: A continuity monitor and indicator circuit for monitoring the continuity of a segment of a pair of control conductors along which a control current flows includes capacitors at each end of the segment being monitored, which capacitors are connected to bridge the conductors and provide an a.c. electrical path between the conductors. A transformer has its secondary winding connected in series with one of the control conductors in the segment and an oscillator is connected to the primary winding of the transformer. The oscillator arrangement is such that it will provide an output signal when the closed a.c. electrical loop formed by the secondary winding of the transformer, the control conductor segment, and the bridging capacitors is broken. A detector is responsive to the oscillator output to detect such output and supply a detector output to a delay means which, in turn, provides an alarm output after receipt of the detector output for a predetermined period of time.

Abstract: A circuit arrangement for digitally indicating the frequency to which an AM/FM radio receiver is tuned in which the oscillations of the AM and FM oscillators are amplified and converted to rectangular oscillations whose frequency is counted by means of electronic counters and then digitally displayed. The oscillations of the AM oscillator and the oscillations of the FM oscillator are amplified and converted to rectangular signals by means of a common broadband amplifier which has a sufficiently broad bandwidth so that the oscillator frequencies for the AM range as well as those for the FM range are both passed and amplified, and the coupling of the input of the broadband amplifier to the outputs of the tuning oscillators is so loose that the tuning oscillators are not noticeably detuned by changes in capacitance of the broadband amplifier. The common broadband amplifier includes two inverters which are each designed as an integrated circuit, and have a fast rise-time.

Abstract: A selectively tunable heterodyne receiver including a plurality of frequency conversion stages which can be tuned to a desired receiving frequency by the use of two voltages which control the coarse and fine tuning adjustments and wherein the first voltage is supplied to a first injection oscillator to control the harmonic output of a crystal controlled harmonic generator and wherein the second voltage is supplied to a second injection oscillator which is continuously variable within a frequency range corresponding to the frequency spacing between the adjacent harmonics of the harmonic generator and wherein the second oscillator is stabilized to the desired adjusted frequency.

Abstract: A short wave broadcasting receiver which can receive accurately and stably the desired station is formed with a local oscillator which comprises a variable frequency oscillator, reference frequency oscillators, premixers and band pass filters, frequency converter and an 1F amplifier. By adding a frequency counter unit comprising a frequency counter block and digital display block, the received frequency can be digitally displayed stably and correctly by using a cheap low speed frequency counter.

Abstract: A phase locked loop includes a variable frequency oscillator, a phase comparator for comparing the phase between an output signal derived from the variable frequency oscillator and a reference signal and for generating a control signal in response to the phase difference between the two signals for controlling the variable frequency oscillator, an indicator for indicating the phase difference between the signals, and a control circuit for varying the frequency of the variable frequency oscillator.

Abstract: The present invention relates to an indicator arrangement for indicating the condition of a phase locked loop. The indicator comprises a flip-flop having its two input terminals connected directly to the input terminals of the phase detector of the phase locked loop in a manner such that under a lock condition the signal at the first input terminal of the flip-flop will be advanced in phase from the signal at the second input terminal. Under such condition a first output signal will be generated at a first output terminal of the flip-flop to activate a "lock" indicating device. When out of lock, the signal at the second input terminal of the flip-flop will be advanced in phase to the signal at the first input terminal and (a) a second output signal will be generated at the first output terminal causing deactivation of the indicating device, and (b) a first output signal will be generated at a second output terminal to activate a no-lock indicating device when desired.

Abstract: A resistor is connected to the source of a C-MOS inverter included within a crystal oscillator circuit in order to reduce the power dissipation in the crystal oscillator circuit. A switching transistor is connected in parallel to said resistor, said switching transistor being responsive to an LED display switch for enabling LED display or an illumination lamp switch for illuminating a liquid crystal display. The switching transistor shunts the resistor in response to actuation of the LED display switch or the illumination lamp.

Abstract: A dual time constant, phase lock loop indicator is described which will respond in one manner to signals indicating an "unlocked" condition and respond in another, different manner to signals indicating a "locked" condition.

Abstract: A digital logic level signal indicates whether a first signal in a phase-locked loop is locked in phase and frequency with a second signal provided to the loop. The digital logic level signal is provided from the sequentially last stage of a counter having a predetermined number of stages. The counter counts cycles in an input signal corresponding to one of the first signal and the second signal. A reset signal pulse having a first predetermined duration is provided to the counter from a pulse width discriminator when the pulse width discriminator detects a phase difference between the first and second signals of greater than a second predetermined duration. The reset signal pulse resets the counter. The digital logic level signal is in a state indicating an in-lock condition when a predetermined number of input signal cycles occur without the counter being reset.

Abstract: Apparatus for indicating whether a correlation tracking system such as a phase-locked-loop has locked onto a periodic signal or not, utilizing a quadri-correlation circuit and digitalizers for the in-phase and the quadrature correlation signals, and logic circuitry for detecting the direction of transitions in the output state combinations of the digitalizers, and for adding the detector output signal rates for obtaining lock.

Abstract: A received, suppressed carrier, quadraphase shift key modulated (QPSK) signal is demodulated with a phase locked loop including a variable frequency, coherent reference that drives first and second channels also responsive to the QPSK signal. The channels respectively derive first and second replicas of binary signals that modulated the suppressed carrier. The replicas are combined to derive a variable amplitude error signal for controlling the coherent reference frequency. The frequency of the coherent reference is dithered at a low rate so that there is derived a relatively low level tracking error phase from the locked loop. The frequency of the coherent reference is swept when the phase of the error signal differs from the dithering phase by a predetermined value that is appreciably less than 90.degree..

Abstract: A high frequency variable oscillator has its frequency grossly set by a bandswitch and an uncalibrated coarse tuning control and finely tuned by an uncalibrated incremental control. The oscillator includes a broad band buffer circuit and a push-pull output circuit to provide an amplified isolated output having attenuated even harmonics. The oscillator includes a user programmable digital counter element connected to count the output of the oscillator. The counter includes timing circuitry and a multiple stage programmable ripple counter timed thereby. Each stage of the counter is connected to a latch decoder which is in turn connected to a digit display element. The latch decoders are connected to be controlled by the timing circuitry.

Abstract: A narrow-band tone decoder has a controllable oscillator, connected in a fast-capture phase-locked loop, for generating a signal having a frequency determined by a control signal produced within the loop. A synchronous detector, which responds to an input signal of the tone decoder and to a signal from the controllable oscillator, produces a signal having a magnitude dependent upon the magnitudes of the input signal and of the signal from the controllable oscillator. A window comparator monitors the control signal within the loop for deciding when the generated signal is within a predetermined frequency range.

Abstract: To provide the required multiple channels for an aircraft communications system, a crystal controlled reference oscillator includes a tunable circuit for changing the base reference frequency provided by a crystal. The base reference frequency of the crystal controlled reference oscillator is pulled in frequency by changing the capacitance shunting the crystal. Two transistor switches change appropriate capacitors in series with the usual oscillator capacitor to obtain the capacitance values needed to pull the base reference frequency and thereby provide additional reference frequencies. The transistor switches are controlled by pilot actuated controls that operate a sliding display mark over a digital frequency indicator.

Abstract: A phase lock detector for a digital frequency synthesizer. The frequency synthesizer includes a programmable digital frequency divider for the output signal, a reference frequency Fr oscillator and a phase lock loop which controls the frequency of the synthesizer output by comparing the phase of the frequency divider signal with the phase of the reference signal. The frequency Fr of the synthesizer is determined by programming N in the relationship ##EQU1## The phase lock detector includes logic means providing a "window" which is "open" for a count which is symmetrically less than and more than the factor M. The detector does not signal "out-of-lock" condition as long as output from the programmable divider occurs during the time the detector window is open.

Abstract: A display panel or console is mounted in the driving compartment of the vehicle in a position to be observed by the driver and provides status information regarding, for example, the operability of the headlights or taillights, and position information concerned primarily with the position of the trailer relative to the cab and whether there is a "jacknife" condition. The system may also check the status of truck tire pressure and brake drum temperature to determine if the pressure is too low or the temperature too high. The lights, for example, are checked by monitoring the continuity to the filament. The existing lines to the lamp are pulsed with a filtered square wave signal and a resistance sensor determines continuity; a lack of continuity causing illumination of the associated status lamp of the display panel. In another arrangement a memory circuit is associated with each indicator circuit so that a fault condition is stored and remains stored even if corrected.

Abstract: An unlocked detector for a digital delay lock loop employs an up-down cour which periodically accumulates the algebraic sum of the quantized positive and negative adjustments made at a preselected rate by the incremental phase modulator. Whenever this sum reaches a specified threshold value corresponding to a particular phase error, an unlocked indication is given. Arrangements utilizing the same principle are disclosed for analog loops.