Abstract: Apparatus for detecting the occurrence of an arc during a spark erosion process is based upon the principle that the noise component of the voltage across the discharge gap disappears when an arc occurs. The noise voltage is detected and compared with a reference voltage in a discriminator circuit. A signal from a logic circuit is also applied to the discriminator which determines the presence of a current through, and of a voltage across, the spark discharge gap.

Abstract: A noise-slicing device for substantially eliminating the noise from an input signal consisting of signal pulses riding in a background of noise The input signal is fed through an electronic attenuator into an output comparator which provides an output whenever its input-signal level is above a reference voltage, 2 Vref A feedback loop provides a control signal to the attenuator to automatically control the attenuation level The input to the feedback loop is the output of the attenuator The loop comprises comparator means providing an output when the attenuator output signal is above its reference voltage, Vref, a one-shot multivibrator, summing means having -Vref as one input and the M-V output as the other, an integrator and a limiter, the attenuator control signal being the output of the integrator

Abstract: A field effect semiconductor device including a plurality of field effect semiconductor elements formed on a common substrate and a compensating circuit for controlling the threshold voltage of said transistors by comparing the threshold voltage of one transistor to a reference voltage and generating a backward bias control voltage across a PN-junction of the one transistor between the source thereof, which is connected to the source of at least one of the other transistors, and the common substrate.

Abstract: A liquid or solid medium is acoustically examined to detect or measure the concentration of a selected entrained particle matter of different acoustic impedance than the medium and given average particle size by transmitting through the medium to acoustic transducer means acoustic wave energy of a selected frequency such that the wave energy is attenuated by scattering and diffraction by all the constituents of the medium down to and including the particle size of the selected matter, and comparing the transducer output voltage produced by the incident wave energy with a reference transducer output voltage produced by acoustic wave energy which is attenuated by all the constituents except the selected particulate matter to obtain a resultant voltage representing the concentration of the selected matter. This resultant voltage may be utilized to drive a meter or recorder for displaying concentration and/or an alarm for signalling a critical concentration. One disclosed embodiment of the invention is a single frequency system for use in applications where the medium contains only the selected particulate matter to be detected and employs an external reference voltage source. A second disclosed embodiment is a multiple frequency system for use where the medium contains more than one particulate matter and utilizes a transducer output as a reference voltage. A primary application of the invention involves measuring the concentration of oil in water.

Abstract: An electronic current monitoring system and method in which a current in a transmission line is detected, converted to an output voltage representative of the value of the current and compared with reference voltages representative of minimum and maximum current values in the transmission line. An alarm signal is generated in the event that the output voltage drops below the minimum reference voltage or rises above the maximum reference voltage. Two or more alarm currents can be monitored simultaneously, each alarm current representing a different condition at a subscriber station with a separate alarm being given for each alarm current which represents a different condition at the subscriber station. An alternating current signal can be impressed on the transmission line and detected with the frequency thereof compared to predetermined values to detect tampering with the alarm system. An alarm is activated in response to an alarm signal in the event the frequency in the line changes from the predetermined frequency value. The reference voltages are adjustable to adjust the tolerance level from the normal current and, in addition, alternate reference voltages are coupled to the system by a switch so that different reference voltages can be switched into the line to quickly change the level of current being monitored.

Abstract: The video signal in a low light level television camera is fed to a first operational amplifier which continuously integrates this signal to produce an indication of the average value of the intensity of light in a viewed scene. The video signal is also applied to a pair of circuits that detect and store the peak values of the video signal in alternate fields formed by the scanning electron beam in the camera pick-up tube. During formation of one field, the peak value of the intensity of light in the viewed scene is detected and stored in one circuit while the stored indication of the peak intensity of the light detected by the other circuit during the preceding field is integrated in a second difference amplifier. The output voltage of the second amplifier is a measure of the difference between the stored peak voltage applied thereto and a reference voltage. This difference voltage is passed by a diode switch to a summing amplifier where it is combined with the average value signal from the first amplifier if the peak value signal indicates that the intensity of light from the viewed scene exceeds a prescribed peak reference light intensity. The combined signal is applied to a voltage translator which produces signal voltages of the correct polarities for varying the gains of image intensifier and vidicon pickup tubes of the camera inversely with respect to changes in the intensity of light from the viewed scene.

Abstract: An analog to digital converter of the dual slope type, employing a high gain input amplifier as both a buffer and integrator and a second high gain amplifier as a comparator. The input voltage is coupled to the non-inverting input terminal of the integrator through a capacitor. A programmed switching circuit provides for switching of the coupling capacitor either to the input voltage or to an input common terminal and also provides for opening and closing a direct feedback loop from the comparator output and for switching the second input terminal of the integrating amplifier between a reference level and ground. The converter operates to charge the integrator capacitor for a fixed time at a rate proportional to the input voltage and then to discharge this capacitor at a rate proportional to the reference voltage, while a counter accumulates time base pulses, until the capacitor reaches its initial level, the accumulated counts being a digital representation of the input voltage.

Abstract: A minimum valve voltage firing control method and circuit for HVDC thyristor power converter circuit operated in the rectifying mode. The valve of the commutating voltage across the respective thyristor valves is sampled and the minimum sampled value during each valve firing stored on a capacitor through the medium of suitable valve voltage sampling and gating circuits. The stored valve voltage samples are compared to a minimum valve voltage reference value and an error signal derived under conditions where an insufficient valve voltage is indicated. The error signal is employed to increase the minimum angle of delay of firing Alpha to a safe value adequate to assure a sufficient valve firing voltage.

Abstract: A data acquisition system including a plurality of temperature monitoring circuits, each including an operational amplifier having a resistance-type temperature sensing element connected in a feedback loop of the amplifier and operable to provide an output voltage that is a function of the temperature measured by the circuit, a reference source which supplies a reference voltage to the amplifiers, enabling each amplifier to provide a constant current to the sensing element, a reference source monitoring circuit operable to provide an output voltage proportional to the reference voltage, and a multiplexing circuit for selectively extending the output voltages provided by the temperature monitoring circuits and the reference source monitoring circuit to a central processor. The output voltage provided by the reference source monitoring circuit is processed at the central processor to permit adjustment of the output voltages extended to the central processor from the temperature monitoring circuits to compensate for changes in the amplitude of the reference voltage.

Abstract: An apparatus for converting a complex AC voltage wave to an equivalent DC value which is a measure of its true RMS value and which may then be read on an accurate indicating device such as a digital voltmeter, incorporating thermal converters and operational amplifiers in a temperature-compensated configuration The apparatus maintains a portion of an unknown AC voltage wave, which is thermally converted into a DC voltage, substantially equal to a DC reference voltage A portion of a DC output voltage is also maintained substantially equal to the DC reference voltage Since the proportioning means for the complex AC voltage wave and the DC output voltage is the same, the true RMS value of the complex AC voltage wave is equal to the DC output voltage

Abstract: A ground fault detector system for isolated power lines, especially those for use with operating room and intensive care monitoring equipment including an isolated test circuit arrangement for checking the operation of the system, that does not itself introduce potentially hazardous and dangerous ground faults into the isolated power lines being monitored. More specifically, the isolated power ground fault detector system of the present invention functions to alternately connect a detector circuit to the power lines at a frequency which is a submultiple of the source frequency. The detector senses both capacitive and resistive ground faults and provides an output voltage signal representative of the magnitude of the ground fault. This output voltage signal is compared to a reference voltage in a voltage comparator which activates alarms and indicators if the ground fault exceeds a preset threshold value. The system also includes a test circuit for checking the operation of the system which when actuated simultaneously switches the detector system from the isolated power lines to auxiliary power lines and introduces a simulated capacitive resistive fault into either of the auxiliary lines. By this arrangement, the system may be checked without introducing a potentially hazardous and dangerous ground fault into the isolated power line supplying the equipment.

Abstract: There is disclosed a switching circuit with a controllable hysteresis in which the hysteresis is introduced into the circuit through a feedback circuit which is connected to an internal node of the switching circuit. The input to the switching circuit is therefore independent of the hysteresis feedback circuit. The switching circuit is comprised first of a comparator which includes a differential amplifier, a differential-to-single-ended convertor, and ON-OFF biased output circuitry such that when an input signal is above a predetermined reference voltage, the switch is in an ''''open'''' condition and such that when the input signal falls below this predetermined reference voltage, the switch is in a ''''closed'''' or conducting condition. Hysteresis is introduced into the comparator circuit by selectively adding a predetermined amount of current to one or the other of the output nodes of the differential amplifier in the comparator circuit during times correlated with the operating condition of the switching circuit. This additional current raises or lowers the input voltage which is necessary to change the condition of the switching circuit and thus introduces a hysteresis into the circuit. The magnitude of the hysteresis is adjustable by controlling the amount of current delivered to the output nodes of the differential amplifier in the comparator. By the application of the hysteresis-producing current to the appropriate output nodes of the input differential amplifier, the hysteresis can be made to occur to one side or the other of the aforementioned reference voltage. Additionally, the hysteresis may be centered about this reference voltage.

Abstract: The line repeater operating on bipolar PCM signals includes substantially identical circuits for both directions of communication to provide line equalization, clock extraction, and pulse regeneration and retiming. A differential input, differential output operational amplifier has a line compensating network in a feedback path thereof. A peak detector coupled to both outputs of the operational amplifier and an amplitude comparator coupled to the output of the peak detector and a reference voltage produces a control signal to control the line compensating network and thereby compensate for line distortion of the received PCM signals and provide constant amplitude received PCM signals on both outputs of the operational amplifier. The clock extractor includes an average full wave rectifier coupled to both outputs of the operational amplifier, a tank circuit coupled to the output of the average rectifier and a 90* phase shifter and amplitude limiter to produce first square wave timing pulses prederminedly related to the bit rate and the zero crossings of the received PCM signals. The first timing signal has its negative going transistions differentiated and inverted to produce second timing pulses. The pulse regenerator includes a threshold voltage and two decision circuits coupled thereto and to the outputs of the operational amplifier, a different decision circuit being provided for each polarity of the received PCM signal. A different AND gate is coupled to the output of each of the decision circuits and are enabled by the second timing pulses. A different RS flip flop is coupled to the output of each of the AND gates and are reset by the positive going transistions of the second timing pulses. The output of the two RS flip flops are combined to provide regenerated bipolar PCM signals for transmission to the next line repeater. A direct current voltage coupled over the transmission line and a zener diode arrangement provides +V and -V power supply voltages at the repeater. A voltage of + OR - V volts is used in the operation amplifier of both directions of communication, a voltage of +V volts is used in the remainder of the circuits of one direction of communication and a voltage of -V volts is used in the remainder of the circuits of the other direction of communication.

Abstract: An electronic chord organ, in which voltage controlled oscillators are each supplied with the same voltage, the voltage being selected by actuation of keys of an organ keyboard, and the currents supplied to the individual oscillators being selected to sound a musical chord. The voltage controlled oscillators each receive voltages from a resistive voltage divider via a voltage sample and hold circuit, key switches applying voltage from selected points along the voltage divider via diodes to a common bus, the bus controlling the frequencies of all the oscillators, and the diodes serving to render only one key switch operable to apply voltage to the bus when plural ones of the key switches are simultaneously closed.

Abstract: A controlled rectifier is connected in multiple across a nonregulated d.c. source which supplies operating energy to a transistorized d.c. to d.c. converter apparatus. Also connected across the source, oppositely poled, is a Zener diode with a reverse breakdown voltage greater than the normal source voltage but less than the breakdown potential which damages the transistors in the voltage regulator portion of the converter. A gating signal is applied to the controlled rectifier if Zener diode breakdown occurs due to a sustained increase in source voltage. A fuse interrupts the leads from the source when the resulting high current flows through the controlled rectifier and protects the transistors from damage. Another Zener diode is connected, with reverse polarity, across the connections between the regulator and inverter portions of the converter. Its reverse breakdown voltage is selected just above the normal regulated output voltage, but low enough to protect the transistors in the inverter circuits. This second Zener diode also supplies a gating signal to the controlled rectifier, if breakdown occurs, to protect against an overvoltage due to a fault in the regulator circuits. Additional Zener diodes may be used in similar manner to protect against overvoltage faults at other points in the converter apparatus.

Abstract: A control for a step voltage regulator having a reversible motor for actuating a tap changer switch to vary the regulator output voltage when a ''''raise'''' or a ''''lower'''' signal respectively is applied thereto, includes a potential sensing transformer for deriving a sample DC voltage proportional to the regulator output voltage, a zener diode for deriving a DC reference voltage of opposite polarity to said sample voltage, a summing operational amplifier which receives the sample and the reference voltages on its inverting input, a polarity and magnitude sensor including a pair of oppositely-poled, serially-arranged zener diodes coupled to the output of the summing amplifier and a NPN and PNP transistor having commoned bases coupled to the pair of zener diodes for deriving raise and lower signals when the output voltage from the summing amplifier is of predetermined magnitude and of opposite polarity, and a rheostat for varying the gain of the summing amplifier to thereby regulate the voltage bandwidth within which the output voltage of the step regulator is maintained.

Abstract: In this invention a positive voltage V1 and a negative voltage V2 are simultaneously monitored by two voltage comparators, which compare voltages on two potentiometers with a standard reference voltage. The potentiometers are tied between constant current loops, each comprising a zener diode, a resistance, and a transistor. When either of the voltages changes the collector of the appropriate transistor takes up the voltage, and thus the potentiometers shift in their potential in accordance with the change of the monitored voltages. These changes in potential are transferred to the comparators which switch their output from a logical zero to a logical one whenever the voltages they are monitoring vary by more than a selected value from a preselected value.

Abstract: Cable fault locator and method in which a calibrated current of constant magnitude is passed through a conductor to provide a known voltage drop per unit length. The drop across a desired portion of the conductor is compared with a reference voltage which is set by a dial calibrated in units of length. The length of the portion of the conductor under test is read directly from this dial. An ohmmeter and voltmeter are provided for discovering and analyzing faults in the cable, and an adjustable voltage source is provided for cancelling the effects of external voltages on the conductors. The entire system is incorporated in a compact highly portable instrument.

Abstract: An apparatus for monitoring the corrosion rate of meatal in a plant stream by its polarization resistance featuring automatic means to reduce current flow through a metal specimen electrode before subjecting it to programmed polarization potentials. Spurious signals due to circuit oscillation are limited by using a current-to-voltage transducer that introduces essentially zero impedance in the current circuit to produce a functional voltage proportional to specimen electrode current. The functional voltage indicates corrosion rate by meter and alarm, and is inverted and amplified at moderate gain to provide and automatic current reduction signal through an isolating sample-and hold circuit. By a timing sequence the summing point of an operational amplifier receives both an input proportional to the inverted and amplified functional voltage and a continuously transmitted reference voltage from a freely corroding reference electrode during a fist time period. Additional programmed polarization voltages are introduced for summing during a second time period to establish polarization resistance. Circuit stability resulting form the use of low impedance components and restricted transmission of oscillations between circuit loops permits reliable monitoring of the corrosion of a wide variety of troublesome passive metals that form thin oxide films of high electrical capacity.

Abstract: Bipolar analog input signals are tested for apparent polarity, and depending on the polarity indication, the analog signal is either inverted or not inverted and resulting input signal is combined with a constant reference voltage so that the effective input to the analog-to-digital converter will always be a unipolar voltage having a minimum nominal value greater than the potential error of the polarity decision element. A counter or register type output device, which reflects the digital resultant from the conversion, is corrected by subtracting the digital equivalent of the constant reference voltage, either by presetting the counter to an initial negative value or by subtraction following the conversion. The initial polarity decision further controls the readout, either direct or complemented, to correspond to the apparent polarity of the input signal.

Abstract: A circuit which is utilized to produce a reference voltage that is substantially independent of changes in the supply line voltage and in temperature and which produces a regulated output voltage as a function of the reference voltage.

Abstract: A display baseline stabilization circuit is described which automatically compensates for differences in the quiescent DC voltage levels of input signals being displayed on a cathode ray tube or other display device, to maintain the baseline displays of such levels in the same vertical position The stabilization circuit includes a sampling system for sampling the quiescent voltage level of such input signals and comparator means for comparing the sample output voltage with a DC reference voltage corresponding to the desired vertical position of the baseline to produce a difference voltage The difference voltage is stored in a gated correction memory whose output is a baseline correction voltage feedback applied to the output of the sampling gate for subtraction of the correction voltage from the sample output signal transmitted to the display device The stabilization circuit may be employed in a time domain reflectometer apparatus in which a test pulse generator, such as a tunnel diode, applies step voltage input pulses to one end of a transmission line under test to measure the value and location of any discontinuation in the characteristic impedance of such line The other end of such transmission line is selectively terminated in an open circuit, a short circuit, or a finite resistance so that the quiescent DC voltage level of the step voltage input signal varies with such termination changes and tends to cause the display baseline on the cathode ray tube to move vertically However, this movement of the baseline is prevented by the stabilization circuit

Abstract: A circulating pulse code modulation (PCM) encoder utilizes capacitive charge redistribution techniques to obtain a hyperbolic self-companding characteristic. The analog sample to be encoded is used as a charging reference voltage, and, by means of an offset bias source, a zero volt decision level forms the basis for PCM signal emission.

Abstract: A voltage regulator is disclosed for varying the output of a generator of a road vehicle by changing the current flow in its field winding. The voltage regulator device includes, as is common, a Zener diode or equivalent break-down device which, as known, conducts at a predetermined battery voltage, and serves to render a transistor conductive, which transistor, when rendered conductive, acts through further components to reduce the current flow in the field winding. In systems of this type it is commonplace to provide for temperature compensation by providing a thermistor or equivalent device in the circuit. Such device, in a known manner, serves to compensate for changes in battery temperature, as well as for the changes in temperature coefficient of the Zener diode and the transistor so utilized. However, in accordance with the instant invention, such temperature compensation is achieved by means of a simple impedance network interconnecting the Zener diode or equivalent device and the transistor, such impedance network, in effect, serving to multiply the net negative inherent temperature characteristics of the transistor by a selected amount to compensate for the net positive temperature coefficient of the Zener diode, the resultant characteristics of the voltage regulator circuit with respect to temperature being desirably negative or, at least, zero. In the specific preferred embodiment, a resistor is disposed across the base-emitter of the transistor, and another resistor is disposed in series circuit with the Zener diode. The ratio of these two resistors substantially defines a multiplication factor which enhances the net negative temperature coefficient of the transistor and serves to overcome the net positive temperature coefficient of the Zener diode.

Abstract: The invention concerns detection devices for image analysis systems in which an amplitude modulated video signal is obtained by line scanning. A two value signal is obtained by comparing the instantaneous amplitude of the video signal with a reference voltage so that the detector output comprises an electrical pulse each time the amplitude e.g. exceeds the reference voltage. The duration of each pulse is equal to the duration of the excess amplitude excursion.

Abstract: A stop motion system for multi-thread textile machines includes a number of thread slack-detection switches disposed in parallel and each having an indicator lamp and a diode in series with the switch. A voltage source and a stop motion relay are in series with the switches and the voltage source produces a potential through any closed switch and its associated lamp and diode greater than the breakover voltage for the diode. Each diode, however, is a four layer diode so that its sustaining voltage is very much less than its breakover voltage. In this way, the first diode to conduct reduces the potential available across any of the other diodes to the sustaining voltage so that only the first detector circuit activated will be effective to provide an indication of malfunction.

Abstract: A circuit to sense variations in alternating voltage applied to a load and to interrupt power flow to the load on reduction of the applied voltage, including a rectifier to rectify the alternating voltage, a voltage regulator to apply a constant level part of the rectified voltage as the power supply to a Schmitt trigger, part of the rectified voltage controlling conductivity of a transistor that provides the input signal to the Schmitt trigger according to variations in the rectified alternating applied voltage, a Zener diode to reference the Schmitt trigger at a voltage slightly below the voltage applied to the transistor controlling the trigger, a Zener diode at the output of the trigger to control the presence or absence of signals from the Schmitt trigger to a further transistor that controls the gate of a triac connected in the power line to the load, and the triac being gated to a non-conductive state to block power flow to the load upon reduced alternating applied power. Said circuit also can be used to sense variations in direct current voltage applied to a load and to interrupt power flow to the load on reduction of the applied voltage, in which circumstance no rectifier is used and the direct current applied voltage is utilized in the same manner as the rectified voltage when alternating voltage variations are being sensed.