Abstract: A method of detecting timing errors in a system oscillator for an electronic device, such as a power supply, includes the step of comparing a system oscillator signal with a delayed generated signal and generating a signal representative of the timing error when the system oscillator signal is not identical to the delayed signal. An LED indicates to an operator that a timing error has occurred. A hardware circuit implements the above-identified method.

Abstract: A method for detecting the presence or absence of an abnormality in a signal x having a frequency f from a signal source, is implemented by a circuit arrangement for deriving a now signal provided at the present time by the signal source, and for deriving a past signal at a point of time preceding the present time by an interval of time M/f where M is an integer. The circuit arrangement also detects an abnormality in the signal and/or the signal source compared to the new signal and to the past signal. The now signal x.sub.m is provided by the signal source at a point of. Another now-signal x.sup.'.sub.m is provided at a point of time preceding the now time t1 by t-1/4f. The signals Xm and xm are derived as a pair. A past signal x.sub.n corresponding to the signal x.sub.m and another past signal x'.sub.n corresponding to the signal x'.sub.m are also provided as a pair.

Abstract: An electromagnetic intrusion sensor including a sensing element, a first phase shifter circuit for phase shifting an input or oscillation signal in accordance with a capacitance of the sensing element, a second phase shifter circuit for outputting a reference signal having a fixed delay relative to the input or oscillation signal, a phase detector circuit for providing a detector signal having a duty cycle representing the phase differential between the outputs of the first and second phase shifter circuits, and an oscillator circuit for outputting a signal having a frequency which changes according to the duty cycle of the detector signal.

Abstract: The present invention relates to a security device having a control box (12) containing an electronic system (50) and a communications loop (14) over which the system transmits a signal. The device is constructed so that the communications loop can extend from the control box across the boundary of a portal such as a door into a sealed enclosure into which access is restricted whereby the loop must be damaged or moved in order for an entry to be made into the enclosure. The device is adapted for detecting unauthorized entries into such enclosures such as rooms or containers and for recording the time at which such entries occur for later reference. Additionally, the device detects attempts to tamper or interfere with the operation of the device itself and records the time at which such events take place.

Abstract: A monitoring system for an electronic instrument includes within itself a microprocessor and a watchdog circuit each provided with its own oscillator which generates a clock pulse and operating on the basis of this clock pulse. The watchdog circuit transmits a periodic interrupt pulse to the microprocessor which transmits a response pulse to the watchdog circuit in return. The watchdog circuit monitors the operation of the microprocessor by measuring the phase difference between the interrupt and response pulses and the microprocessor monitors the operation of the watchdog circuit by measuring the period of the interrupt pulse.

Abstract: The invention interfaces a two-wire 60 Hz circuit to two circuits, each unidirectional, sending and receiving, and carrying frequency modulated audio tones containing the amplitude and phase of the 60 Hz voltage impressed on the 60 Hz circuit. The invention is used to interface differential relays used by electric utilities to detect power transmission line faults to a four-wire voice band communication line.

Abstract: System and method for detecting arcing faults in a dynamoelectric machine by monitoring the neutral lead of the machine for a radio frequency voltage produced by arcing, providing a warning signal in response to a change in the radio frequency voltage, and providing a shutdown signal in response to a radio frequency voltage greater than a predetermined level. An RF voltage coupler is capacitively coupled ot the neutrla lead, and a radio frequency monitor connected to the voltage coupler detects peaks in the RF voltage.

Abstract: An apparatus for visually indicating abnormal phase relationships between incoming or outgoing phases for a plural phase device, comprised of a plurality of light emitting means interconnected between phases by a logic circuit arrangement whereby the various combinations of on/off indicators present a coded, visual presentation representing the specific mismatch condition of the network. The invention encompasses the concept of incorporating the indicating circuitry within the multiple phase device enclosure and providing an aperture in the enclosure so that the indicators may be viewed without the necessity of gaining access to the interior of the device and exposing individuals to the danger of high voltage/current circuits.

Abstract: To detect the phase signal, particularly for alternators of motor vehicles, with simple and inexpensive measures, an active rectifier is employed, which supplies at the output a signal with constant polarity (e.g. positive) which can thus be used to verify the correct operation or malfunction of the alternator.

Abstract: A protective apparatus for use in an A.C. electrical power system with a circuit breaker for connecting and disconnecting first and second electrical conductors that are electrically energizable, the conductors normally having a negligible phase difference of electrical energization when the circuit breaker is closed, and the circuit breaker having auxiliary contacts defining the state of the circuit breaker as open or closed. The protective apparatus includes a circuit responsive to the auxiliary contacts for producing a first signal representative of the state of the breaker as open or closed and another circuit connected to the circuit for producing the first signal and operable when the breaker is closed for generating a second signal when the phase difference of electrical energization of the first and second electrical conductors exceeds a predetermined value. A further circuit provides an indication of malfunction of the circuit breaker when the second signal occurs.

Abstract: A phase shifter uses a PIN diode or diode pairs operated in a switching mode to switch transmission-line elements for phase-shifting radio frequency or microwave signals. A drive circuit for each diode(s) includes a FET switch controlled by a first level of a bilevel control signal to apply B+ to forward bias the diode(s) with a forward current. When forward biased, the active region of the diode(s) becomes flooded with charge carriers. The first FET switch is turned OFF by a second level of the bilevel control signal, and a second FET switch is turned ON to apply a reverse bias voltage to the diode(s) to render them nonconductive. Before the diode(s) become nonconductive, the excess charge carriers must be swept out of the diode(s). To achieve fast switching, the second FET switch must draw a large current for a short time as the excess charge carriers are removed.

Abstract: In the field of automated guided vehicles it is particularly important that speed and steering angle feedbacks be accurate and reliable. Any deviations in these feedback signals should be promptly detected and used to alter operation of the vehicle. An apparatus constantly monitors the time varying output signals of a pair of resolvers respectively associated with wheel rotation and steering angle. The loss of either of the resolver signals for more than a preselected duration of time related to the excitation frequency and vehicle speed results in the power delivered to an electric drive motor being discontinued and the vehicle brakes being applied.

Abstract: An electronic apparatus is proposed for detecting variations of significance in an electrical voltage as a function of time. The apparatus includes a tracker (2) of these variations, a comparator (6) comparing the voltage with a reference voltage V.sub.2, and a counting circuit (10, 15, 20). The tracker (2) monitors variations in the voltage supplied to a filtering and rectification system (4), which eliminates the continuous component of the signal and within the high frequency range greatly diminishes the levels of the parasitic signals having an oscillatory character. The comparator (6) furnishes a calibrated pulse (25) each time the voltage exceeds the threshold V.sub.2, and the counting circuit (10, 15, 20) counts the number of these calibrated pulses within a given time period T and furnishes a logic signal (30) if this number exceeds a predetermined quantity.

Abstract: A device for indicating that a refrigerator door is open, includes a housing which is mountable on a refrigerator in the vicinity of the refrigerator door during the use of the device. A transducer is mountable at the refrigerator door gasket for changing an electrical parameter in response to the movement of the refrigerator door from its closed position to an open position. Circuitry disposed in the housing senses the change in the electrical parameter of the transducer to produce an alarm after a preselected time delay.

Abstract: A current sensor for use in a three phase ac system for producing a signal indicative of the average value of the sum of the squares of the ac current and of the phase imbalance between the three phases using two current transducers and an associated method.

Abstract: Apparatus and method for monitoring a self-regulating heater comprising a PTC conductive polymer while it is being powered by a power supply signal. The apparatus is connected to a power supply and to the heater, the heater then producing a heater signal which is fed to a comparator. The comparator deterines the phasal relationship between the power supply signal and the heater signal and indicates when the signals are out of phase by a predetermined magnitude.

Abstract: An apparatus to monitor a circuit in which an AC voltage source is connected to a plurality of paralleled current consuming loads, such as heaters, including a reactive load in parallel with the current consuming loads at a point in the circuit more distant from the voltage source than any of the current consuming loads being monitored, a phase shift detector connected to the current consuming loads and at a point in the circuit between the voltage source and the nearest current consuming load being monitored, the phase shift detector being sensitive to the shift in current phase induced by the reactor load, and an alarm connected to and actuated by the phase shift detector which provides a warning when the phase shift induced by the reactive load is lost, indicative of a failure in the circuit.

Abstract: Apparatus which can be embodied in an electronic wristwatch monitors the integrity of a wrist strap ground. An input terminal to which a known ground is coupled is provided. An oscillator produces a fixed frequency which is mixed with a signal from the input terminal to provide a composite signal. The composite signal is coupled to one input of an exclusive OR-gate. The other input of the exclusive OR-gate is coupled directly to the output of the oscillator. The output of the OR-gate is processed to produce an output signal indicative of the phase relationship between the oscillator output and the composite signal. When the input terminal is grounded, the phase relationship between the oscillator output and the composite signal changes, resulting in a change in the output signal which can be used to trigger an indicator (e.g., visual display and/or aural alarm) to indicate to a user whether he or she is properly grounded.

Abstract: A monitoring arrangement for a gas turbine spark ignition system in which the spark discharge current oscillates at a known frequency includes a sonic sensor accoustically coupled to the spark igniter, a filter for passing only those signals from this sensor which have a frequency corresponding to that of the discharge current and indicating means responsive to the filter output for indicating that the spark igniter is operating. An additional optical sensor may provide a signal response to a spark gap in the ignition system, signals from both sensors being required to energize the indicating means.

Abstract: A circuit is disclosed for monitoring the frequency of a signal for controlling choppers of electric cars. The phase of the control signal is compared by a comparator with the phase of a reference frequency signal produced by a reference-frequency signal generator. When the phase difference which is greater than a predetermined value is sustained continuously for more than a predetermined period of time, an alarm is produced.

Abstract: A monitor for sensing any break in electrical continuity between a body and earth when the body is coupled to earth by way of a grounding tether used to prevent build-up of static charges on such body. The monitor includes an oscillator circuit for generating A.C. output voltages which are adapted to actuate an alarm. Body capacitance and resistance are coupled by way of the tether across an impedance network either in the tuned circuit determining oscillator frequency or in the output load thereof whereby the resistance or inductance of the impedance network provides the path to ground for the body through its tether. With body capacitance and resistance components of the total impedance, variable elements in the impedance network are adjusted to diminish the circuit output voltage below the threshold voltage required to actuate the alarm when continuity exists while developing an output voltage level sufficient to actuate the alarm when a break in continuity occurs.

Abstract: A directional loop antenna array is provided by two flat parallel spaced apart open loops with a shorted turn disposed between the open loops equidistant therefrom. The signals from the open loops are vectorially added and subtracted in a sum and difference circuit and the phase angle between the sum and difference signals is ascertained in a phase detector circuit that feeds an indicator. The so determined phase angle is either greater or less than 90.degree. depending upon the relative magnitudes of the loop signals.

Abstract: A three-phase symmetrical component active band-pass filter includes three 120.degree. phase shift circuits which are connected in a closed loop fashion such that each phase shift circuit receives an input signal from one phase of an associated power system and a second signal from the output of one of the other phase shift circuits. A voltage tunable filter is formed by using multipliers to couple some fraction of the output of each phase shift circuit to a summing point at the input of another phase shift circuit. Phase comparators and an integrator can be added to achieve a self-tracking tuning arrangement.

Abstract: A protective relay for protecting a power system from sub-synchronous current oscillations. The protective relay determines both the amplitude and frequency of sub-synchronous current oscillations occurring in the power system. A series of logic relationships, based in part on the parameters of the power system, are implemented by the protective relay such that when the frequency and amplitude of the sub-synchronous oscillation signal satisfy these relationships a trip signal is produced.

Abstract: An overload-sensing circuit for an electric motor driven by an alternating signal comprises a supply line connecting the motor to a power source, a resistance in the supply line, and a first comparator for measuring the phase relationship between the power source voltage signal and the motor current signal. A variable resistor is employed to select a phase relationship which represents a load limit for the motor. A second comparator compares the measured phase relationship to the selected phase relationship and produces a signal representing an overload condition of the motor when the measured phase relationship generally equals the selected phase relationship.

Abstract: A transducer for converting a pressure variation to a variation in the frequency of a periodic function includes a reference oscillator and a sensor oscillator coupled to a digital mixer. The reference oscillator includes a reference capacitor and reference resistor for providing a reference periodic electrical signal having a frequency which is a function of the reference timing capacitor and reference resistor. Similarly, the sensor oscillator has a variable sensor timing capacitor and a sensor resistor for providing a sensor periodic electrical signal having a frequency which is a function of the variable sensor timing capacitor and sensor resistor. The digital mixer generates a mixed periodic electrical signal having a frequency proportional to the difference between the reference and sensor electrical signals. The transfer function of the transducer relates pressure and frequency and is adjustable by adjustment of the magnitude of the reference and sensor resistors.

Abstract: The present invention relates to a power sequence device which comprises an element which generates a sequencing code which is capable of being decoded by actuators included in the various equipment cabinets. The sequencing code is initiated by a sensing element which indicates the input power has reached a stable threshold whereupon the various cabinets comprising the data processing system are turned on in a desired order. Upon loss of power, the sensing element generates a warning signal indicating an impending power loss thereby enabling the equipment to perform an orderly halt.

Abstract: Means for differentiating between traction current and signal current in an electrified railroad includes a first input transformer providing an input signal of the same frequency and phase as the track signal current. A second input transformer is connected to the track to provide a track signal. There are means for comparing the phase and frequency of the input signal and the track signal and means responsive to an output from the comparison means indicating a correct comparison for providing a relay driving signal.

Abstract: In a radio frequency detector, a high pass filter is provided to attenuate any undesired low frequencies present in signals applied to the filter. The filter output serves as an input to an AND gate. A low pass filter directs power line voltage to a one-shot multivibrator which is biased to respond to the positive-going zero crossing of the power supply to produce an output of limited duration which is applied to the gate as an enabling input. The output of the gate is joined to a second one-shot multivibrator which responds to a pulse generated when the gate is fully enabled causing energization of an alarm actuator.An additional pulse detector optionally is interposed between the gate and the second one-shot to eliminate any random pulses which may occur at the gate output at a frequency below r.f. level, and an additional filter optionally is included between the high pass filter and the AND gate to eliminate the effects on the circuitry arrangement of high frequencies above a predetermined level.

Abstract: The leading edge of each pulse of an incoming signal sequence starts a first monostable multivibrator whose period is equal to the period of the pulse sequence when the pulse sequence has the desired frequency. The input signal sequence and the output signal from the multivibrator are applied to two inputs of an exclusive OR gate. The latter furnishes an output signal corresponding to the difference in pulse width between the signal applied to the two inputs. The leading edge of the difference signal then starts a second monostable multivibrator whose pulse width corresponds to the maximum allowable frequency deviation. The output signal of the second monostable multivibrator is applied to an inverting input of an AND gate. The direct input of the AND gate receives the difference signal. The AND gate, therefore, only furnishes an output signal when the difference signal has a greater pulse width than the output signal of the second multivibrator, i.e.

Abstract: A system for identifying which of the phases of an N-phase electric-power transmission network has experienced an electrical disturbance. For each phase there is produced a first signal representative of the transient variations of an electrical parameter of the respective phase, or of a linear combination of at least two of these parameters. A set of N second signals is generated from the product of two linear combinations of at least N-1 signals selected among the first signals. The sum of all coefficients for each linear combination is set to zero, with each of the second signals being related to a given phase. Each of the second signals is then integrated to produce a set of N third signals associated with the respective phases. A fourth signal is generated by combining all of the N first signals in a symmetrical manner with respect to all of the first signals, such that the fourth signal is independent of the associated phases.

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: Methods and apparatus for on-line detection and measurement of degradation or undesirable changes in the time constants of sensors used in monitoring a system are disclosed. Methods and apparatus of this invention are particularly suitable for use in complex and high-risk industrial processes or other operations where it is undesirable and expensive or dangerous to allow certain parameters of the operation to change above or beyond a predetermined amount. This invention includes a detector for determining when a signal from a sensor crosses a preselected signal level such as for example a zero level. The output of the detector or zero crossing detector is provided to a counter or other means which determines the rate of the zero crossing by counting the number of crossings per a specific time period provided by a timer.

Abstract: A timing waveform generator which provides substantially noise immune timing waveforms in response to a polyphase source voltage suitable for thyristors. Each timing waveform is phase shifted from a reference sine wave using a combination of filtering and hysteresis, to achieve the total desired phase shift angle. The timing waveforms are also logically related to determine improper phase sequence and/or a missing phase.

Abstract: A transistorized detector sensitive to the ripple component of the DC output of an alternator gives a visual or audible warning signal when the ripple component exceeds a predetermined level providing early indication of failure of either a winding or rectifier diode.

Abstract: A method of and a device for monitoring poly-phase currents in poly-phase equipment, in which a phase signal representative of the current in each phase of the equipment is obtained, the phase signals multiplexed so as to obtain a single multiplexed signal, and the multiplexed signal then processed to extract from it an output signal or signals representative of, for example, overload, unbalance, earth fault or short circuit conditions.

Abstract: The supervised conductive loop comprises a plurality of switch elements connected in series with a DC current source. Encoder modules are located in parallel with each of the switch elements. The encoder module comprises an oscillator and an impedance element. When a switch element is opened, the oscillator associated with that switch is energized and places an AC signal on the loop. The frequency of each oscillator uniquely identifies the associated switch element. The impedance element, formed by a resistor and a capacitor, is used both as a filter for the power supply voltage to the oscillator as well as a bandpass filter to permit oscillator signals present on the loop to bypass open switch elements and be detected at any location in the loop. Frequency identifying means are coupled to the loop to permit an indication of which oscillators have been operated.

Abstract: An FSK receiver for a single channel analog telemetry system comprises an FSK demodulator, a frequency multiplier, and a frequency-to-voltage converter. An FSK transmitter comprises a voltage-to-frequency converter, a frequency divider, and an FSK tone generator. The principal advantages of this system are greater speed due to faster settling time and reduced errors in accuracy and linearity.

Abstract: An automatic transfer control device for generating signals to cause associated circuit interrupters to selectively energize an electrical distribution system from either of a pair of electrical power sources. The device includes an over- and under-frequency monitoring circuit to determine if the power source frequency is within preset limits. The frequency monitoring circuit includes a zero-crossing detector which activates a clock oscillator, the output pulses of which are accumulated by a counter for one half cycle. The number of pulses occurring during the half cycle is compared with a limit value stored in a read-only memory. An alarm signal is activated if the number of pulses accumulated is out of limits.

Abstract: An alarm system for detecting a dangerous condition such as the increase in content of or the presence of toxic or inflammable gas in the air and giving a warning signal. The alarm system comprises an AC power supply, a full-wave rectifier connected to the AC power supply and rectifying alternating current from the AC power source into direct current. An AC bridge circuit connected to the AC power supply and includes a sensor element at least in one branch. An AC operational amplifier is supplied with power from the full-wave rectifier and receives an input signal which is the output signal delivered from the bridge circuit through a DC blocking capacitor. A thyristor is connected in parallel with the AC power supply, with its control gate connected to the output of the operational amplifier, and its main electrodes in series with an alarm indicator actuable when the thyristor is triggered into the conduction state.

Abstract: A capacitive shift fire detection device having a sample circuit and a reference circuit, each circuit having an air capacitor connected to an oscillator and a counter. The presence of particles of combustion in the ambient environment results in a change in the dielectric constant of the air dielectric of the sample capacitor, thus changing its capacitance. This change in capacitance is detected by an oscillator in the sample circuit, the mismatch of oscillators in the two circuits causing an exclusive OR-gate to go high, activating an alarm system.

Abstract: Process for the automatic signalling of faults of an automatic static safety module and a module realizing said process which can be used in automatic safety systems which can, for example, be used in nuclear reactors.The module comprises at least one pair of identical parallel logic circuits each having a first positive continuous supply connection and a second negative supply connection. The circuit output can have one or other of two logic states depending on whether it is connected to the first or second connection. It comprises means for the automatic signalling of a fault in one module component constituted by a.c. voltage sources of different frequencies inserted in the supply connections. It also comprises means for detecting the presence of beats between the a.c. voltages appearing at the outputs of circuits and for indicating cases of non-agreement of the logic states.

Abstract: Protective relay apparatus which includes monitoring and detecting functions related to subsynchronous currents in a three-phase electrical power system. The monitoring function provides signals related to the positive sequence component of any subsynchronous current flowing at a monitored subsynchronous frequency. The detecting function is responsive to the signals provided by the monitoring function, distinguishing between subsynchronous currents due to self-excited oscillations, and those due to transient oscillations, to provide a timely trip signal for a circuit breaker in either instance.

Abstract: A phase unbalance detecting system that includes also low-voltage detection and wrong-phase-sequence detection. The system can be packaged in a small volume because it is a solid state type that uses a minimum of electronics and does not require transformers for obtaining signals from the several phases of the plural-phase power line but only one transformer for the D.C. power supply circuit for the detection system. The system incorporates means for allowing it to be used at 50 or 60 Hz without separate adjustment, for making it insensitive to noise and harmonics of the power line, and for providing a good estimate of the negative sequence voltage caused by a phase unbalance. It provides external terminals whereby it can be adapted for use at different power line voltages.

Abstract: A circuit for generating an indication in response to the occurrence of a predetermined condition is characterized by means for detecting the occurrence of the condition and for generating the indication after the condition has existed for a selected time. In a preferred embodiment of the circuit, the condition to be detected is a warning signal preceding a radio broadcast of a severe weather report, and the circuit includes an input stage for receiving the signal and for generating a control voltage which increases in value with increasing duration of the signal. The control voltage is applied to an input to a multivibrator, and after a first period of time increases to a value sufficient to place the multivibrator in an oscillating state.

Abstract: A symmetrical component sequence filter which provides a signal responsive to a predetermined sequence quantity of an electrical power system, while using only one phase shift other than 180 degrees. A single reactive element provides the phase shift. A single adjustable resistor calibrates the filter when the reactive element is non-precision. Selecting a precision reactive element eliminates even the single adjustment. The symmetrical component sequence filter enables both a positive and a negative sequence component to be simultaneously derived from common processing circuitry, requiring only one additional reactive element.

Abstract: Circuitry for attachment to a radio receiver to monitor and test a detected intermediate frequency signal and an audio signal from a demodulator portion of the receiver to determine whether a transmitted radio frequency signal is within frequency tolerances and modulation limits and to provide an alarm, either visual or audio, when the limits or tolerances are exceeded. An off frequency monitor tests the DC component of the radio demodulator detected IF signal and includes input signal conditioning circuitry for filtering the audio signal, high impedance for minimal loading of the radio, and level shifting. Upper and lower level voltage references indicate maximum permissible frequency deviation from the nominal transmitting frequency. Upper and lower level comparators compare the conditioned direct current (DC) signal to the respective voltage references and provide a changed output state upon an out of tolerance transmission.

Abstract: Apparatus for detecting the presence of subsynchronous current components in an electrical generating or transmission system is disclosed. Input signals, representative respectively of line voltage and current, are conditioned and initially filtered to suppress high frequency noise. The input voltage signal is further limited and filtered to produce a constant amplitude, sinusoid reference. The input signals are then multiplied to yield the subsynchronous current signal components, if any, which undergo further filtration by a bandpass filter circuit. In addition, the detection apparatus is provided with circuit means for insuring protection against overvoltage and current surge conditions.