Abstract: A calibration circuit for a solid state electricity meter comprises a plurality of resistors formed on an integrated circuit. The resistors are connected by an on-chip array of electrically controlled switches, such as MOSFETs, to signal processing circuitry driving the meter. The resistors establish variable voltage divider networks which compensate the meter for phase, gain and offset errors distributed in the signal processing circuitry. The values of the variable voltage divider network may be established automatically during testing of the meter, by a digital computer, or semi-automatically, by a technician, to establish the "on" and "off" states of the various transistors of the array.

Abstract: Calibrating errors of a variable gain amplifier used in an AC calibrator or a meter for measuring AC are determined for a gamut of frequencies. The gain of the variable gain amplifier is varied by adjusting the value of a variable resistor in discrete steps. A variable amplitude signal is applied to the amplifier while the resistor is adjusted in discrete steps so the amplifier derives a gamut of variable amplitude signals that are supposed to have predetermined values. The amplitudes of the gamut of variable amplitude signals derived by the amplifier are detected and compared with the values that the signals are supposed to have to derive a calibrating error signal of the amplifier for each variable resistor value. A gamut of variable frequency, constant amplitude signals is applied to the amplifier while the amplifier gain is constant. The amplifier has a tendency to derive an AC output signal having a different amplitude in response to different ones of the frequencies.

Abstract: Apparatus whose measurement means consists solely of electronic components, measures the power taken by an electrical load connected to an alternating source of electricity supply in such a manner that the power sensed or energy accumulated is in agreement with the same measurements as performed by a conventional rotating disc electromechanical meter. Fundamental frequency filtering means when applied to either one or both supply voltage and load current ensure that the electronic circuitry performs the appropriate measurements in determining power consumption. A single sample per mains cycle applied to load current and supply voltage is sufficient to measure power consumption, energy consumption accumulation, and produce accumulated energy pulses appropriate to measurement of real power, true power and volt-ampere power consumed by the load.

Abstract: An electrical peak value measuring and evaluating apparatus including a transmitting circuit for transmitting peak values to an output, restoring circuit for restoring the level in the transmitting circuit to a known value after reaching a peak, and a retaining circuit for retaining the restored signal at the known value until the input signal again rises above a predetermined level.

Abstract: An electric power measuring device wherein input analog signals representative of instantaneous values of current and voltage are applied to a multiplier (23) and the product applied to a converter (35, 37, 41, 43, 45, 47) to provide a pulse output signal having a frequency representative of the product and hence of the level of power consumption. Compensation for offset errors in the multiplier is effected by periodically reversing the polarity of one of the inputs to the multiplier and effecting corresponding reversals at the input to the converter to avoid irregularities in the output pulse rate when the level of power consumed is low.

Abstract: The method of measuring an electric energy supplied to a load comprises sampling the value of a load voltage or current a desired number of times, converting each of the sampled analog values to a digital value by an A/D converter, accumulating the digital values obtained correspondingly to the number of times of such sampling actions, dividing the accumulated value by the said number to calculate an average value per sampling, and correcting the offset in the A/D converter by the average value thus obtained.

Abstract: A signal processing device having a level adapter circuit, in particular a broad band oscilloscope, having an operational amplifier with an amplification factor determined by the ratio of a first resistor between the signal input and the inverting input of the operational amplifier--the virtual ground--and a second resistor between the inverting input of the operational amplifier and the signal output, in which the resistors may optionally be complex, in which at least one parallel resistor is provided for the first resistor, the first terminal of which is firmly connected to the signal input or a connecting point of a plurality of partial resistors forming the first resistor, and the second terminal of which can be switched over between the inverting input of the operational amplifier, which input forms the virtual ground, and the real reference potential for the amplifier input.

Abstract: Apparatus for measuring current over a wide range generates an eight bit accurate, 16-bit dynamic range digital signal from a current transformer secondary. Two signals proportional to the rectified secondary current, one generated by a large burden resistor and the other by an amplifier with programmable gain and an overrange indication, are applied through a multiplexer to an eight bit analog to digital converter which has three selectable reference voltages. A microprocessor selects the input signal, converter reference voltage, and one of four levels of amplifier gain which provide the greatest resolution for the magnitude of the current being measured, and provides an appropriate scale factor, from 2.sup.0 to 2.sup.8, for the eight bit accurate digital signal generated by the analog to digital converter.

Abstract: An electronic watthour meter employs a first analog signal representing either a load current or voltage to pulse-width-modulate a second analog signal representing the other of the load current or voltage. The resulting signal contains a DC component proportional to the product of current and voltage. AC components are removed from the product signal in an integrator before applying the DC component to a threshold circuit. The threshold circuit alternates its output between positive and negative values each time the DC component of the product signal passes through a predetermined positive and negative value. This pulsed signal is transmitted to a register for integrating the energy usage. A pulse-width modulator produces a constant-frequency pulsed output whose positive and negative alternations have lengths which are proportional to the line signal it receives. At each alternation of the pulsed signal, the output of the pulse-width modulator alternates between a direct and an inverted signal.

Abstract: Calibrating errors of a variable gain amplifier used in an AC calibrator or a meter for measuring AC is determined for a gamut of frequencies. The gain of the variable gain amplifier is varied by adjusting the value of a variable resistor in discrete steps. A variable amplitude signal is applied to the amplifier while the resistor is adjusted in discrete steps so the amplifier derives a gamut of variable amplitude signals that are supposed to have predetermined values. The amplitudes of the gamut of variable amplitude signals derived by the amplifier are detected and compared with the values that the signals are supposed to have to derive a calibrating error signal of the amplifier for each variable resistor value. A gamut of variable frequency, constant amplitude signals is applied to the amplifier while the amplifier gain is constant. The amplifier has a tendency to derive an AC output signal having a different amplitude in response to different ones of the frequencies.

Abstract: Current-measuring device including a non-contacting current sensor and an evaluating device connected downstream to the sensor for producing an output signal proportional to a current being measured, comprising a circuit arrangement for determining a zero drift of at least one of the evaluating device and the current sensor from symmetrical components of the current being measured and for correcting the drift.

Abstract: A system for circulating hot or cold liquid through a pad placed in thermal contact with a patient for thermal therapy. The system includes a flexible thermal pad with an internal channel for carrying the liquid and a pump assembly for circulating and optionally heating the liquid. The patient-contacting surface of the pad comprises a foam having a cushioned surface to reduce the risk of ischemia and enhance patient comfort. An open-cell foam structure absorbs and retains moisture for applying moist heat. The system is microprocessor controlled and includes a heater to warm the liquid to a selectable temperature for heat therapy. A display selectively indicates set-point or actual liquid temperature in either .degree. F. or .degree. C. as desired. Safety features include three separate over-temperature sensors, a tilt switch and a float switch which de-energize both the heater and the pump when an abnormal temperature is sensed, the unit is tipped or a low liquid level is sensed, respectively.

Abstract: A method and an apparatus for measuring settling characteristics of a device under test. A measurement system for measuring an input signal by sampling and digitizing that input signal is employed to obtain reference data by measuring a reference signal, at least one level of which is flat, and to obtain measurement data by measuring a second signal representing the settling characteristics to be measured but containing an error component due to inclusion of the measurement system itself. The error component is removed from the measurement data by adjusting the timing and level of the reference data relative to those of the measurement data.

Abstract: Calibrating a plurality of digital-to-analog converters using a calibration memory for storing calibration characteristics for respective digital-to-analog converters so as to provide uniform analog responses to digital data, and a calibrator to receive original digital data and to adjust it utilizing the stored calibration characteristics to produce adjusted digital data that, when inputted into a digital-to-analog converter, produce an analog signal that corresponds to the original digital data.

Abstract: A sensor is periodically energized and the sensor output is amplified, the amplified signal being applied to two sample-and-hold circuits which are alternately activated in response to the sensor drive, one being activated only when the sensor is energized and the other being activated when the sensor is not energized. One of the samples is subtracted from the other in a summer for cancelling the amplifier offset. The summer output may be buffered, and there is also applied to the summer an offset correction signal for cancelling sensor offset and buffer offset inaccuracies.

Abstract: A watthour meter having a Hall component in a sensor circuit connected to a low voltage type of voltage-to-frequency converter, achieves linear signal conversion of the voltage output from the sensor circuit with maximum polarity reversal of the Hall voltage by synchronizing such polarity reversal with polarity reversal across an integration capacitor of the converter so that the amplified offset voltage produced by the integration operation and the effects of capacitor instability compensate for each other.

Abstract: A new sensor means for accurately measuring the current flowing in an electronically controlled switch is presented. An ac coupled current sensor is arranged in circuit with the electronically controlled power switch. The output of the sensor channel is zeroed (or restored to another fixed independent level) whenever the power switch is in the OFF condition. Using the natural modulation of the power switch itself to coordinate the reconciling of the sensor output level with the OFF state of the power switch helps restore to the dc level lost through ac coupling. This coordination of the sensor with the switch itself reduces dc offset and drift and allows ac coupling, which removes dc common mode and increases primary current sensor flexibility, all without adding complexity. A plurality of such sensors can be combined to measure indirectly the load current from a plurality of switches according to Kirchoff's Current Law.

Abstract: A high frequency probe for a logic analyzer adapted to operate with different types of logic circuits, and signals which may or may not be superimposed on a dc component. After an input capacitance, a high frequency amplifier feeds both an output terminal and a compensator circuit which compares the deviation between low frequency or dc components appearing at the input and output terminals, and compensates for the deviation by reinjecting a signal at the input of the high frequency amplifier. Variable attenuation may also be also be included between the high frequency amplifier and the output terminal.

Abstract: In an analog test system for testing integrated circuit chips, AC level calibration is achieved by adding a minimal number of new elements and more fully utilizing elements existing in the system. A reference voltage from an existing precision DC power source is fed to an analog switching device. A control signal is also fed into the analog switching device from an existing digital signal generator. Based on the control signal, the analog switching device converts the reference voltage into a rectangular waveform signal, which is then digitized. The digital signal is analyzed, and data from the digital signal is compared with reference data, and the AC level error, if any, is determined. AC level calibration is based on this error.

Abstract: A current-comparator technique for obtaining a load loss standard with adjustable loss tangent (or power factor) for in-situ calibration of transformer loss measuring system is described. The load loss standard, driven by the test voltage through a low-loss high-voltage compressed-gas-dielectric reference capacitor, simulates an inductive load which can be operated with load currents of up to 1000 A. For a 500 kV reference capacitor and a load current of 1000 A, the load loss standard simulates an equivalent inductive load with a rating of 500 MVA. Adjustment of the loss tangent (or power factor) is achieved by comparing the load current, using the current comparator, with in-phase and quadrature reference currents derived from the test voltage.

Abstract: Electronic trip units employed within static trip circuit breakers are individually calibrated and automatically adjusted to ensure that the trip transfer characteristics are within specification requirements. A trimming network within the trip unit circuit contains a plurality of parallel resistors each separately connected within the circuit by means of a fusible link. Test input and output values are compard to idealized values that are binary-weighted within a look-up table in the test equipment computer. The percent correction required is determined and the appropriate links are interrupted to provide ideal trip response.

Abstract: A switched-capacitor integrator is employed in an electronic watthour measurement device for integrating the average component of a product signal formed by pulse-width modulating an analog signal proportional to one of a load current and voltage at a pulse duty ratio proportional to the other of the load current and voltage. A hysteresis comparator forces the direction of integration to alternate between positive and negative limits for balancing out offset voltages in the integrator and comparator. A triangular-wave generator employed as part of the pulse-width-modulation technique is also implemented using a switched-capacitor integrator. The switched-capacitor integrators permit fabrication of the circuit with the required accuracy without needing external, discrete time-constant-determining resistances and capacitances. Measurement accuracy is determined by the ratio of capacitances of two on-chip capacitors, the accuracy to a clock signal and two reference voltages.

Abstract: A circuit for providing DC bootstrapping to an AC amplifier integrates a sample of the output of the amplifier and feeds the result of that integration to the input of the amplifier, thereby driving the input of the amplifier to a zero potential level. The integration can be accomplished by an operator amplifier and a capacitor in a feedback circuit.

Abstract: Measurement accuracy of an oscilloscope is extended by monitoring the temperature within the oscilloscope, and automatically entering a calibration cycle if the temperature varies by a predetermined amount. A temperature sensor is strategically located within the oscilloscope to sense variations in temperature. A first sensed temperature value is stored. Upper and lower temperature limits representing the maximum permissible deviation from the stored value are calculated. Instantaneous temperature values from the sensor are compared with the stored value, and as long as the instaneous values are with the limits, an indication of extended accuracy is provided. If the instantaneous temperature values vary outside the limits, an automatic calibration cycle is initiated. After calibration, a new temperature value is stored and the monitoring process continues to ensure extended accuracy.

Abstract: An electric power measuring device wherein input analogue signals representative of instantaneous values of current and voltage are applied to a multiplier (23) and the resulting product signal is applied to a converter (35, 37, 41, 43, 45, 47) to provide a pulse output signal having a pulse rate representative of the product, and hence of the level of power consumption. The converter is of the kind including a capacitor (35) which is charged during successive periods of equal duration by the product signal and a much larger reference signal which reverses at the end of each capacitor charging period until the capacitor charge does not reverse in polarity during a charging period, so that reversal of charge on the capacitor is assured during the next charging period, whereafter the direction of the reference signal is again reversed at the end of each charging period.

Abstract: A system for calibrating an energy meter is provided. The energy meter has a rotor which rotates at an angular velocity generally proportional to the energy input to the meter. A reference transducer receives an energy input for generating a reference signal having a predetermined parameter, such as frequency, generally proportional to the energy input. A test apparatus is responsive to rotation of the rotor to generate a test signal having a predetermined parameter, such as frequency, generally proportional to the angular velocity of the rotor. An error signal generator receives the reference signal and the test signal upon fractional rotation of the rotor and generates an error signal to indicate the amount of error between the frequency of the test signal and a calibration value corresponding to the frequency of the reference signal. The meter is calibrated based on the error signal. A related method is also disclosed for calibrating the meter.

Abstract: A method for locking scales to a waveform display uses reference points from the waveform to determine starting scale points. Based upon the starting scale points and the characteristics of the waveform the scales are calculated. Any changes in gain in the waveform are applied to the scales so that the scales change in direct proportion to the waveform. The field/line numbers of a television video signal are tracked and displayed on the waveform display to identify that portion of the waveform relative to a picture frame which is being displayed.

Abstract: In a method for the elimination of the d.c. voltage components of a capacitive a.c. voltage divider whose a.c. measuring voltage which may include a d.c. voltage component, is fed to a measurement transformer, the task is to be solved to remove as quickly as possible the d.c. voltage component of the a.c. measuring voltage also to the greatest extent possible without falsification of the reproduction of the middle or high voltage to be measured. This is achieved in that the a.c. measuring voltage (U.sub.M) is fed to a measuring amplifier (14) by way of two parallel lines (L1, L2) via a d.c. voltage blocking element (6). The a.c. measuring voltage (U.sub.M) is thereby fed directly by way of one line (L1) and the d.c. voltage component (U.sub.G) of the a.c. measuring voltage (U.sub.M) is determined in the other line (L2) in that the a.c. measuring voltage (U.sub.M) is subdivided into such small time sections (t) that an equal number of time sections is coordinated per cycle (T) or half cycle (T/2) and the a.c.

Abstract: A probe body for a measurement system comprises a probe-tip terminal for connection by way of a probe tip to a test point, a cable port for connection by way of at least one cable to a measurement instrument, probe circuitry, a function generator, and a switch. In a first state of the switch, the input terminal of the probe circuitry is connected to the probe-tip terminal and in a second state of the switch the input terminal of the probe circuitry is connected to the function generator. When the switch is in the second state, the function generator may be used to impress a signal having a predetermined waveform on the probe circuitry.

Abstract: A method and apparatus for automatically calibrating the deflection of an electron beam in a graticuled cathode ray tube. The apparatus includes a microprocessor and digital-to-analog converter for generating input signals of a predetermined accuracy and sending the signals to an amplifier of a cathode ray tube to deflect the electron beam across graticule lines on the faceplate. A phototransistor optically coupled to the faceplate detects the electron beam coinciding with the graticule and in response generates an electrical signal. Signal processing circuitry processes the signal to remove noise from it and retrieve detection signals. The microprocessor receives the detection signals from the signal processing circuitry, compares each detection signal to its corresponding input signal, and adjusts the gain and offset of the amplifier in response to the comparison. Additional circuitry digitally records the beam position relative to the graticule lines.

Abstract: Disclosed is a battery powered, hand-held self-contained electronic tonometer with a digital readout for displaying pressure in millimeters of mercury. The tonometer includes a transducer which is a solid state pressure sensitive element and which produces a voltage proportional to intraocular pressure. An electrical waveform is produced by gently bringing the transducer in contact with the cornea. The waveform is converted to a digital signal and processed by a single chip microprocessor. The baseline of a reference signal is nulled by equalizing the charges on two capacitors on the inputs of two differential amplifiers. Equalizing the differential inputs of the two amplifier stages results in a gain of zero and removes any carrier signal. Microprocessor software detects the baseline condition established by equalizing the differential inputs. The microprocessor then looks for a series of valid measurements and calculates the average intraocular pressure along with an estimate of reliability.

Abstract: The present invention is an arrangement for measuring electrical power. The arrangement comprises a conductor traversed by an electrical current i and a voltage-to-current converter for transforming an electrical voltage u.sub.N into a proportional supply current i.sub.N for a Hall element. The Hall element is adapted to produce an intelligence containing output signal .+-.u.sub.H proportional to the product (.+-.i.u.sub.N) of the current i and the voltage .+-.u.sub.N. The Hall element is arranged in an air-gap of a ferromagnetic core that is excited by the current i. A voltage-to-frequency converter transforms the Hall element output voltage .+-.u.sub.H into a proportional output frequency. The voltage-to-frequency converter includes a capacitor for integration purposes and at least two signal sources. The power measuring device also includes a switch for periodically switching a signal proportional to the signal .+-.u.sub.H and for switching said signal sources to compensate for an offset voltage.

Abstract: A method of digital process variable transmitter calibration includes the steps of sensing the process variable (PV) to produce an analog output which is converted to a digital signal representation. The digital signal is corrected by a microprocessor using a characterization equation previously individually developed during a manufacturing testing of the process variable transmitter over a predetermined range of environmental stimuli to ascrtain the coefficients for a polynomial in the form of PV=A.sub.o =A.sub.1 P+A.sub.2 +. . . A.sub.i P.sup.i. Thus, the digital computer produces a process variable representation as a modified digital output. Subsequently, the digital output from the computer is converted to a conventional 4-20 mA analog signal for use as a process control signal.

Abstract: A method and apparatus for converting an electrical signal into a proportional frequency is disclosed. Modulation of the output frequency resulting from polarity switching cycles having half-periods of unequal duration and capacitor voltages which might be non-zero at the time of polarity reversal are substantially avoided. This permits faster and more precise calibration.

Abstract: The electrical measuring meter comprises a polarized motor magnet mounted for movement to and from a starting position, a polarized holding magnet operative magnetically to influence the motor magnet constantly towards such starting position, and a calibrating element magnetized by the holding magnet to effect a partial cancellation of the holding magnet's influence on the motor magnet as is needed for calibration. The calibrating element preferably is in the form of a soft iron circular disc, and soft iron discs of different sizes are used to calibrate the meter for respective different maximum scale current values. Also, the high magnetic permeability of the soft iron disc enables the use of a rugged and economical sleeve bearing mount for the motor magnet even in a meter calibrated for low current measurement.

Abstract: A small field probe is calibrated by selectively varying the field intens and frequency and recording the data in arrays with each incremental step. The arrays are built by selectively varying one parameter while maintaining another constant. In this way coefficients of the equation for the calibration of the probe is arrived.

Abstract: A self calibrating electronic instrument for measuring a physical quantity. The instrument generates an internal correction signal that forces its output to zero whenever it is determined that no physical quantity is present for measurement. The correction signal so generated is preserved and continuously applied as a correction signal during intervals when measurements are being performed.

Abstract: An ac measuring instrument automatically compensates an input attenuator to achieve precision frequency response. The output of the input attenuator is applied to both the conventional measurement portion of the instrument and to an amplifier of variable gain. The output of the variable gain amplifier drives either a resistive or capacitive impedance coupled to the output of the input attenuator. The impedance is thus driven by a voltage that is a scaled replica of the output of the input attenuator. That scale factor may vary from near zero to greater than one, and the impedance acts as a virtual trimmer whose apparent value varies as the scale factor of its actual value according to the gain established for the variable gain amplifier. The proper gain therefor is determined by a servo loop that applies a test pulse to the input attenuator and subsequently samples the output thereof at least twice.

Abstract: A measured signal is supplied to an indication section through a high-frequency amplifier, a frequency converter, and an intermediate frequency amplifier. A predetermined local oscillation signal from a local oscillator is supplied to the frequency converter. A reference signal generator generates harmonic pulses having a uniform level at a spectral interval substantially equal to or larger than the predetermined passband of the intermediate frequency amplifier, the uniform level being used to calibrate a level of the signal to be measured. A frequency setting section sets the frequency of the measured signal. A first switching section switches an input to the high-frequency amplifier to an output side of the reference signal generator in accordance with the frequency set by the frequency setting section.

Abstract: An automatic compensation circuit for use with an analog multiplier is disclosed. At regular intervals at least one input to the analog multiplier is constrained to be zero for a short time. During this time a sample and hold circuit retains the pre-existing output voltage and a feedback circuit is activated which adjusts the output voltage of the multiplier to zero, thereby providing an accurate multiplied or product signal, typically representing power consumption, which is adjusted or compensated for the effects of any internal errors occurring within the analog multiplier.

Abstract: An improved digital servo indicator of the continuous null-balance potentiometric type is disclosed which includes a microcomputer to provide a digital readout of the measured results in the desired engineering unit, or to use the readout in further calculations as desired. The indicator includes a digital-to-analog conversion means using a cascading series of circuits each having a precision resistance element and a pair of MOSFETs for selectively connecting a constant reference voltage to the output through the resistance element to produce the desired analog output.

Abstract: An oscilloscope vertical calibration system is provided in which gain control elements in one or more vertical input channels are automatically controlled with respect to cursor voltages applied to the vertical output amplifier. Such calibration process is performed for each deflection factor setting either manually or automatically and the correct gain control signals are stored in memory.

Abstract: There is provided by this invention an electronic circuit for interfacing with a magneto-optical current sensor employing the Faraday effect to measure current in a high voltage transmission line. A DC biasing voltage is applied to the output of a photodetector to substantially eliminate the DC component providing a substantially AC output signal to the circuit. There is also provided a negative low pass error feedback to self-calibrate the circuit.

Abstract: A mechanized system distributing the access, test and communication functions to the point of testing, typically the centralized switching facility serving the telephone loops and equipment to be tested. Computer (200) stores information about each subscriber loop in the geographical area served by a system. Front-end computers (220,221) interact with computer (200) to retrieve pertinent data regarding loops to be tested. Each switching facility in an area includes a loop testing system (e.g., 160) that implements the required functions. The communication functions residing in front-end computers (220,221) and loop testing systems (160,161) are coupled via a data communication network (140) in a manner that allows any front-end computer to communicate with any loop testing system. Users of the system control access and test from consoles having the capability of establishing independent communication paths over the national dial network for interactive tests on loops accessed through standard test trunks.

Abstract: An improved solid state semiconductor integrated circuit electronic watt/watthour meter circuit having analog and high frequency digital outputs with automatic error correction. The meter comprises first and second transformers for developing first and second voltage and current indicating signals for supply to a multiplier circuit that multiplies the two signals together and derives an output analog product signal representative of the instantaneous power being supplied by a source of electric energy. A multiplier low pass filter circuit is coupled to the output from the multiplier circuit for deriving from the product signal an average value power signal V. An analog-to-pulse rate converter is supplied with the average value power signal V and serves to convert it into a high frequency train of output signal pulses wherein each output signal pulse represents a predetermined quantized amount of electric energy.

Abstract: An analog to digital conversion method and apparatus includes the use of a scaling circuit 15 to scale the magnitude of an analog signal D applied to ADC 4 to within an acceptable input range. A calibration circuit 16 generates a signal M indicative of the effect of the scaling circuit 15 upon a digital signal E produced by the ADC 4. An adder 14 adds the calibration signal M and the digital signal E of ADC 4 to yield a digital output signal N which is the digital representation of measured analog input signal A.

Abstract: A mechanized system distributing the access, test and communication functions to the point of testing, typically the centralized switching facility serving the telephone loops and equipment to be tested. Computer (200) stores information about each subscriber loop in the geographical area served by a system. Front-end computers (220,221) interact with computer (200) to retrieve pertinent data regarding loops to be tested. Each switching facility in an area includes a loop testing system (e.g., 160) that implements the required functions. The communication functions residing in front-end computers (220,221) and loop testing systems (160,161) are coupled via a data communication network (140) in a manner that allows any front-end computer to communicate with any loop testing system. Users of the system control access and test from consoles having the capability of establishing independent communication paths over the national dial network for interactive tests on loops accessed through standard test trunks.

Abstract: A mechanized system distributing the access, test and communication functions to the point of testing, typically the centralized switching facility serving the telephone loops and equipment to be tested. Computer (200) stores information about each subscriber loop in the geographical area served by a system. Front-end computers (220,221) interact with computer (200) to retrieve pertinent data regarding loops to be tested. Each switching facility in an area includes a loop testing system (e.g., 160) that implements the required functions. The communication functions residing in front-end computers (220,221) and loop testing systems (160,161) are coupled via a data communication network (140) in a manner that allows any front-end computer to communicate with any loop testing system. Users of the system control access and test from consoles having the capability of establishing independent communication paths over the national dial network for interactive tests on loops accessed through standard test trunks.

Abstract: An integrating circuit for generating control signals representing watt-hour consumption for connection to an electronic watt-hour meter. The circuit includes a Hall effect sensor for sensing watt-hour consumption, a circuit for integrating the sensed watt-hour consumption, and a circuit for compensating for DC offset voltage generated by the Hall effect sensor.

Abstract: A precision circuit for measuring electrical currents, of the order of only a few pico-amperes, in the individual ionic channels of biological membranes, comprising a pipette engaging a membrane and having an internal electrode connected to a current-to-voltage converter; the converter output is integrated and fed back to a reference potential source for the converter to control that reference potential so that the average pipette electrode is maintained at zero over a predetermined time interval. In the preferred construction the time constant of the feedback integrator is adjustable between a "slow" value and a "fast" value; at the "slow" setting the long-term average of the pipette current is forced to be zero, whereas at the "fast" setting it is possible to measure the potential at the pipette tip at zero current.