Abstract: A lamp control circuit particularly suited for scale illumination in cathode-ray tube display devices provides stabilized lamp control impervious to temperature fluctuations for either constant or pulsed operating modes.

Abstract: An instrument for use in indicating SC/H phase of a composite video signal comprises a display device for providing a polar display. A device generates a first input signal for the display device from the reference subcarrier burst of the video signal so as to cause the display device to display an indication at a predetermined angular position of the polar display. The time difference between the sync point and that zero crossing of the extended subcarrier wave which is closest to the sync point is determined, and is used to generate a second input signal for the display device such as to cause the display device to display an indication at a position of the polar display that is angularly spaced from a predetermined axis of the polar display by an angle given by the fraction having as its denominator the period of the reference subcarrier wave and as is numerator the product of the time difference and 360.degree..

Abstract: A waveform memory circuit samples an analog waveform at regular intervals to generate and store in a first random access memory digitally encoded data points representing the waveform magnitude. Only data points minimally different in magnitude from the most recently stored data point are stored. The number of sampling periods between successively stored data points is counted and stored in a second random access memory. Provisions are made for external control over data acquisition cycle start, the number of data points to be stored, sampling frequency, and difference minimum required to initiate storage.

Abstract: A high speed arrangement for generating smooth lines of consistent thickness regardless of slope in a raster type display system such as a computer graphics system. A digital differential analyzer is employed for determining Y-position information to n bits of fraction for each integral step in X within a single operative clock cycle. All pixel positions are identified that are relevantly proximate to the starting end point of the line, to the concluding end point, and each one-dimensional array of at least three contiguous pixel positions encompassing a cross-section of the interior portion of the line. Intensity values are determined for each such identified pixel position based upon its distance from the true line, with the intensities of the pixel positions identified in each array being additionally determined based upon the slope of the line.

Abstract: An oscilloscope vertical amplifier with Boolean combinatorial trigger generator capability is disclosed. While the display output is fully analog, the trigger output to the time base is digital with a user selectable Boolean function of the analog input signals. Also included is nested triggering, edge as well as level sensitivity, and a trigger filter to selectively inhibit high frequency events. The delay times of the analog and digital signal paths are matched by means of analog delay lines before presentation by a visual display to present the analog and digital signals in time coincidence to the oscilloscope main frame.

Abstract: A thermometer-to-binary encoder converts a quantity I of input digital signals, each representing one bit of an I-bit thermometer code, into a set of output digital signals each representing one bit of a corresponding binary code. The input signals are grouped into a quantity J of signal subsets, the Nth signal subset comprising the input signals representing the Nth lowest order bit of the input thermometer code and every Jth bit thereafter, each subset thereby representing a separate thermometer code derived from the I-bit input thermometer code. Each signal subset is applied as an input to a separate thermometer-to-binary encoder stage which converts the signal subset thermometer code input into a corresponding binary code output. The binary code outputs of every encoder stage are then summed to produce the set of output signals representing the binary output code corresponding to the I-bit input thermometer code.

Abstract: A 50% point of amplitude and phase detector. A differential amplifier produces non-inverted and inverted signals representative of a periodic input signal. Respective sample and hold circuits sample the levels of the non-inverted and inverted signals at predetermined points and the difference is input to the differential amplifier to equalize the position of those signals. The crossover of the non-inverted and inverted signals is detected by a gated differential amplifier whose output controls an oscillator from which the gating signal is derived to lock the phase of the oscillator output with the phase of the periodic signal.

Abstract: A dual rank sample and hold circuit and method is particularly applicable to deglitching the output of a digital-to-analog converter. One signal path is provided for coupling an input signal to the output of the sample and hold circuit to track the input signal during sampling. A second signal path is provided for coupling the input signal to a storage capacitor for charging or discharging the capacitor to the level of the input signal. In one embodiment the output is coupled simultaneously via the first signal path to the input signal and through a resistor to the storage capacitor, during a sampling phase, the capacitor being coupled to the input signal, and thereafter only to the capacitor during a hold phase, the capacitor being decoupled from the input signal.

Abstract: A method and an apparatus provide an optical switching system (10) which provides independent of viewing angle two system optical transmission states of substantially contaminant-free light. The system includes first and second light gates (12 and 12') of which each has associated therewith contaminant light intensity patterns (48 and 66) with points of local maxima (54, 56, 58, 60, 68, and 70) and local minima (62 and 72) in two system optical transmission states. The contaminant light intensity patterns are oriented so that the points of local maxima and minima of the contaminant light intensity patterns of one of the light gates generally align with the respective points of local minima and maxima of the contaminant light intensity patterns of the other light gate. The alignment of contaminant light intensity patterns blocks the transmission of contaminant light in two system optical transmission states, and thereby provides improved viewing angle performance.

Abstract: A field sequential color display system incorporates a color switch which includes a zero to half-wave optical retarder and pleochroic filters to provide an image with high color contrast and resolution over a broad range of display sizes. In a preferred embodiment, a liquid crystal cell which operates between two states of optical retardation comprises the variable retarder to provide a color switch with substantially reduced optical response times.

Abstract: A transmission path is monitored for its suitability for transmission of digital data by transmitting over the transmission path a video test signal which includes a horizontal sync pulse and at least one half-cycle of a generally sinusoidal pulse occurring at a predetermined time after the sync pulse, the generally sinusoidal pulses being inverted in alternate lines or alternate fields of the video test signal. The signal received at the other end of the transmission path is displayed on an oscilloscope-type CRT device having its horizontal sweep triggered by the horizontal sync pulse, so as to superimpose the alternate generally sinusoidal pulses. The configuration of the generally eye-shaped area resulting from such superimposition depends on the suitability of the transmission path for transmission of digital data.

Abstract: The suitability of a transmission path (16 or 18) for transmission of digital data is monitored by transmitting a test signal over the transmission path. The test signal is composed of a succession of video signal lines each including a horizontal sync pulse and a pattern of digital 1's and 0's at a predetermined frequency and occurring on each line at the same data positions relative to the horizontal sync pulse. The patterns comprise a reference pattern of alternating 1's and 0's and test pattern of 1's and 0's at random or in a sequence known to be disruptive to the transmission path. The test signal is received and is displayed on a waveform monitor (28) with the reference pattern and the test pattern interleaved with the complement of the reference pattern and complement of the test pattern, so that the four patterns are superimposed and enclose a generally eye-shaped area.

Abstract: An apparatus and method are provided for automatically calibrating sweep waveforms produced by a sweep generating circuit in response to digital time reference words produced by a system controller. Time interval measurements are made directly on sweep waveforms and sweep slope values are derived therefrom. The sweep slope values are used by the system controller to adjust the digital time reference words.

Abstract: A self-arming, prescaling frequency counter system comprises an armable frequency counter, an envelope detector, a prescaling pulse-shaper, and a delaying means. The envelope detector detects occurrence of an oscillating signal to be frequency measured and transmits an arming signal to arm the frequency counter for the duration of the oscillating signal. The prescaling pulse-shaper is coupled to receive the oscillating signal burst and generate a pulsed test signal of frequency an integer fraction of the oscillating signal frequency. The delaying means couples the test signal to the armable frequency counter input, delaying receipt of the pulsed signal burst until after the counter is armed, and delaying termination of the pulsed signal until after counter is disarmed.

Abstract: A circuit configuration is provided for reducing noise sidebands in the output of an oscillator due to modulation of the oscillation signal by characteristic noise produced by the amplifying element. A gallium arsenide field-effect transistor that produces characteristic noise is operated as a linear amplifier. Positive feedback to the input of the amplifier is provided by a resonator. The amplitude of the oscillation signal is limited by a distinct limiting circuit in the feedback loop, the input to which is isolated from the amplifier by a high pass filter, thereby divorcing the non-linear limiting function of the oscillator from the amplifying function where noise is generated.

Abstract: A line filter for a power supply includes a differential amplifier which is driven from across an inductor in series with a principal current carrying path of the power supply. The differential amplifier output is connected to a capacitance returned to ground for canceling common mode interference as may be generated in the power supply.

Abstract: A digital acquisition system includes a high-speed sampling gate with analog memory for sampling input signals. The samples are converted to digital representations and stored in a digital memory. The digital representations are selectively recalled from the digital memory and fed back as estimators to the sampling gate's analog memory. Since the estimators are essentially the previous samples for each point of a given waveform, the stored waveform converges to the input waveform very quickly, facilitating accurate waveform replication. Embodiments for both sequential sampling and pseudo-random sampling are provided. Operational techniques of the digital acquisition system include noise reduction, loop gain determination, adaptive filtering and signal averaging.

Abstract: A method of comparing first and second data acquired asynchronously allows an effective comparison therebetween even if aliasing errors have occurred during acquisition thereof. Bits of the first and second data are compared in groups of three to obtain relationships therebetween. These relationships indicate if first data is equal to the second data, or the first data can be shifted right and/or left to achieve the second data. This comparison is repeated on successive groups of bits, but the comparison bits used in each data are shifted by a bit for each comparison. If any relationship indicates that the first data was shifted right (or left), then all other comparisons must indicate that the first data matches or is shifted right (or left), for the first data to be found the same as the second data. The presence of both right and left shift relationships indicates that the first and second data cannot be the same.

Abstract: A circuit (11) for use in an associative memory device, one such circuit being associated with each word location in memory, for indicating a match when the word associated with a given circuit (11) is a match for a current portion of a search pattern and the previous word is a match for a previous portion of the search pattern. In operation of the circuit (11), a latch (23) is initialized to a match condition, and provides a match output, which is also applied to the next successive circuit, for the next successive word in memory. The latch (23) is controlled by an AND gate (21), to which is applied the output signal from the circuit for the previous word in memory and a signal indicating a match or non-match for the word in memory associated with circuit (11) containing AND gate (21).

Abstract: An ink jet printer includes a compact ink drop generating module (10) comprising an ink jet print head (14) mounted to a body (12) which contains high and low frequency ink pressure transient suppressing mechanisms (90, 68, 80). These mechanisms inhibit the ingestion of air into print head (14) and formation of print head clogging air bubbles. The body (12) also includes a purgeble bubble trap (72). Head (14) may be of the air assisted type. Air supplied to the head pressurizes ink at one side (82) of the diaphragm (80) and at the other side (84) of the diaphragm to increase the fluid capacitance of the diaphragm. The module (10) is easy to replace as a unit.