Abstract: An active low-pass filter especially suitable for inclusion in an integrated circuit and capable of operating at frequencies up to at least f.sub.T /.beta. of transistors within the filter. A bootstrap circuit is coupled to the emitter follower to reduce the capacitive effect of the emitter follower on the passed signal and to guarantee precision pass band gain match among the filters. A plurality of active filters may be connected across the signal path to provide a selection of bandwidths. A filter is switched into and out of the signal path by selectively enabling and disabling its current source.

Abstract: A current sensing circuit senses current and signals if such current exceeds a predetermined level within an etched circuit board. The circuit comprises a conductive trace of a predetermined resistance within a metallization layer of the board and a reference voltage circuit and comparator coupled to the trace. The reference voltage circuit senses voltage at first sense point on the trace and offsets the voltage a predetermined amount to form a reference voltage. The comparator senses voltage at a second sense point on the trace and compares it to the reference voltage. So long as the second voltage exceeds the reference voltage, the comparator indicates that the current is below the predetermined level. If the second voltage drops below the reference voltage, the comparator generates an output signal indicating that the current has exceeded the predetermined level.

Abstract: A hollow enclosure has first and second ceramic walls interconnected and hermetically sealed by first and second compact coupling assemblies. In one form, each coupling assembly includes a first flange portion, a web portion and second flange portion. The first flange portion of the first coupling assembly is fritted to a first annular edge of the first ceramic wall. The first flange portion of the second coupling assembly is fritted to a second annular edge of the second wall. The second flanges of the coupling assemblies are then placed against one another and laser welded, without the need for thermal clamps.

Abstract: An error correction circuit (16) corrects errors in the thermometer code (T.sub.1 -T.sub.7) developed by a parallel or "flash" analog-to-digital converter (10). The error correction circuit employs plural similar bit exchange modules (34) of which each includes a 2-input OR gate (46) having common inputs (48 and 50) that constitute the inputs of the bit exchange module. The output (52) of the AND gate and the output (54) of the OR gate constitute the outputs of the bit exchange module. The bit exchange modules receive the digital-to-analog converter thermometer code and are interconnected to correct errors therein resulting from the presence of more than one transition between different logic states for adjacent bits in the thermometer code. The error correction circuit manipulates the thermometer code bits to provide a corrected thermometer code (T.sub.1C -T.sub.7C) that has only one transition between different logic states for adjacent bits thereof.

Abstract: An active load network for a device under test includes a logic circuit for anticipating the output state of the device under test and for turning on either a current source of a current sink to properly load its output. The current sink and current source each comprise a pair of CMOS transistors connected in series. One of each transistor pair turns on to either source or sink current and the other provides a variable impedance controlled by the voltage at its gate to regulate the amount of current. A pull-to-center transmission gate is also provided which pulls the output of the device under test to a level between a logic high and logic low when it is turned off.

Abstract: A modified BNC connector for connecting an active probe to an active probe to an electronic instrument includes a female BNC input on the instrument for cooperatively mating with the male BNC output of the probe. The female BNC input includes a flex circuit mounted on a planar surface and disposed about the periphery of its outer coaxial shield. A plastic bezel fits over the flex circuit to permit access to contact points located thereon and to mask the remaining area. The male BNC connector is located in a housing which includes a set of spring loaded telescoping pins which make contact with the flex circuit contact points. The housing includes a rotatable knob that locks the male and female portions together.

Abstract: A variable impedance driver network comprises a plurality of transmission gates connected in parallel between a voltage source and an output. Each transmission gate has a predetermined nominal impedance and by turning on selective gates the overall impedance of the network may be adjusted to match that required at the output.

Abstract: A touch panel has panel scanning signals selectively applied to the four sides of a touch sensing surface of the panel so as to establish alternating current voltage gradients in desired directions across the touch sensing surface. When the panel is touched, touch signals result and are utilized by a touch location circuit in determining the location of touch. The impedence touch current resulting from a user's touch may also be determined and used. The touch panel circuit automatically compensates for any variations in touch signals which occur when the touch panel is untouched and automatically nulls the touch signals under such circumstances to enhance the accuracy of touch location determination.

Abstract: A computer-based instrument system is provided for progammably configuring a variety of computer-based test instruments for performing a variety of tests and permitting high speed execution of tests through concurrent operation of individual test instruments. The instruments are implemented on circuit boards and mounted in a chassis including permanent backplane wiring interconnecting the instruments and a timing and triggering control unit. The backplane wiring includes a conventional computer bus for carrying instructions from a master controller to each instrument and lines for a common system clock signal, protocol signals, and trigger signals between selected instruments and the timing and triggering control unit for synchronizing the operation of the instruments when performing a test. The timing and triggering control unit is adapted to programmably control instrument triggering according to individual test requirements without modification of backplane wiring.

Abstract: Apparatus for providing an indication that a color represented by a color video signal having a luminance component Y and two color difference components R-Y, B-Y is validly reproducible on an RGB color display device. A resistive matrix converts the Y, R-Y, B-Y components of the color video signal to three primary color components R, G, B. Comparators compare the amplitude of each primary color component with predetermined minimum and maximum values, and an OR-gate produces a gamut error signal if the amplitude of one or more of the primary color components is outside the range established by the corresponding predetermined minimum and maximum values. The gamut error signal is applied to a display modifier which modifies the luminance and color difference components to produce a visually distinct effect on a waveform or display monitor. Alternatively, the gamut error signal may be applied to, for example, a color shutter incorporated in the waveform or display monitor to modify the color of the display.

Abstract: A silicon controlled rectifier (SCR) is connected between a selected electrode of a CRT and a reference potential level that is negative relative to the selected CRT electrode. The SCR remains non-conductive so long as the voltage between the selected electrode and the reference potential level remains below the breakdown voltage of the SCR and the SCR's dv/dt rating is not exceeded. If the voltage between the electrode and the reference potential level increases at a rate that exceeds the threshold rate for the SCR, the SCR turns on and shorts the selected electrode to the reference potential level.

Abstract: A programmable sweep generator for generating a linear ramp signal of different slopes in a predetermined step sequence is disclosed. The programmable sweep generator comprises a controllable voltage generator, a voltage-to-current converter, and integrator sections. The slopes of the ramp signal may be electronically controlled by switching the controllable voltage generator, voltage-to-current converter and timing capacitors in the integrator section. The use of independent buffer amplifiers, independent control circuits, and current steering devices for each timing capacitor eliminates the need to connect a switching element in series with each timing capacitor, thereby eliminating any error or non-linearity.

Abstract: An address computation system for updating starting addresses of data arrays in an array processor within an instruction cycle. A first set of registers is provided for storing starting addresses for each array. A second set of registers is provided for storing current addresses for each array. Logic is provided for initially providing, at the beginning of a series of computation steps to be executed repetitively, an address from a register in the first set of registers, changing that address, and storing it back in the same register and in a corresponding register in the second set, thereby updating the starting address for the next repetition of those computational steps while advancing the current address to the second of those steps.

Abstract: A high performance color cathode ray tube is manufactured by welding a shadow mask under very high tension to a metal ring brazed to the tube envelope. The shadow mask material has a high yield strength and a thermal coefficient of expansion near that of the ceramic ring portion of the envelope to which it is secured.

Abstract: A trigger holdoff system for an oscilloscope is provided in which a desired trigger signal is taken out from a repetitive group of raw trigger signals with variable time therebetween. A trigger generator generates raw triggers which clock a divide by N counter programmable by a microprocessor. When the counter reaches its terminal count, a trigger is passed on to sweep or acquisition circuits from the trigger holdoff system and an enable signal is set so that the next raw trigger reloads the counter.

Abstract: A pulse measurement circuit for measuring timing parameters includes main and delayed trigger generators and a timer for measuring the time between generation of the two trigger signals. The circuit further includes an adjustable delay circuit that senses the main trigger signal and in response enables the delayed trigger generator for triggering after a selectable delay. To measure a timing parameter of a pulse, both trigger generators are first caused to trigger on the first parameter boundary and the time between generation of the two trigger signals is measured. The delayed trigger generator is then caused to trigger on the second parameter boundary while the main trigger generator again triggers on the first parameter boundary. The time difference between generation of the two trigger signals is again measured. The first time is subtracted from the second time to measure the time of the pulse parameter.

Abstract: A beam detection apparatus for sensing the position of an electron beam within a cathode ray tube is disclosed. The apparatus includes a photodetector for optically detecting the intersections of the electron beam with a graticule line on the faceplate of the cathode ray tube. In a second embodiment, an electrically conductive pattern of reference markers is applied to the graticule for intercepting the beam and a detector is coupled to the conductive pattern for detecting the interception. Calibration circuitry is also included to generate input signals to deflection amplifiers coupled to the cathode ray tube and to evaluate detection signals generated by the beam coinciding with a graticule line. The calibration circuitry compares the input signals to the input signal value represented by the graticule line and adjusts the deflection amplifiers of the cathode ray tube accordingly to cause the beam to coincide with a graticule line bearing a predetermined relationship to the input signal deflecting the beam.

Abstract: A new and efficient method for attaching an optical fiber to a substrate to form a structurally secure optical fiber package is disclosed. The method first involves coating an optical fiber with an external layer of gold. A silicon retaining member is then provided having a groove therein sized to retain and receive the coated optical fiber. The silicon retaining member and optical fiber are then positioned on a substrate preferably constructed of alumina. Deposited on the substrate is at least one metal pad having an external gold layer on which the silicon retaining member is placed. The optical fiber, silicon retaining member, and substrate are then heated at a temperature sufficient to form a silicon/gold eutectic alloy between th silicon of the retaining member and the gold layers of the optical fiber and pad. Such heating involves a temperature of at least 370.degree. C. Heating is preferably accomplished using a resistor secured to the underside of the substrate.

Abstract: A touch panel input apparatus including two arrays of light detectors placed on the opposite sides of the display device screen and four light sources, each of which is placed at a corner and at angle to illuminate at least the entire array of the light detectors on the opposite side. The light detectors are scanned in synchronization with the selection of the light beam sources. A controlling microprocessor has stored in its memory four sets of data, one for each light source, regarding ambient light condition and beam interrupt thresholds for the light detectors. By software, two equations representing a line are determined and solved to obtain a cross point which corresponds to X-Y position of the finger on the screen.

Abstract: A wideband amplifier with active high-frequency compensation includes an active equivalent RC network connected across the emitters of a differential amplifier. The active RC network exploits inherent junction capacitance and resistance, and is controlled in such a manner that the desired compensation value is provided.