Abstract: A counting circuit includes a digital counter for counting the pulses of an input signal during a counting interval and a pair of digital latches for latching the binary state of the input signal at the beginning and end of the counting interval, respectively. The latched binary states of the input signal and the pulse count of the digital counter are evaluated by an interpreter such as logic circuitry or a microprocessor. The interpreter resolves the pulse count into half clock cycles by comparing the binary states and in response adjusts the pulse count by the addition or subtraction of half a clock cycle.

Abstract: A switch device comprises a support member having at least first and second stationary contacts thereon. An armature is mounted on the support member by means of a body of elastomeric material that is attached to both the support member and the armature. Deformation of the body of elastomeric material allows the armature to pivot relative to the support member between a first position in which electrically-conductive material of the armature establishes electrically conductive connection between the stationary contacts and a second position in which the armature is spaced from at least one of the contacts. At least one permanent magnet is carried by the armature. An electrically-driven switch actuator is mounted stationarily relative to the support member and has first and second energization states.

Abstract: A voltage-controlled current source produces two output current signals whose difference is linearly related to an input voltage signal. The source includes an input buffer and a reference buffer each coupled separately to a current mirror and also coupled together across a current transmitting resistor. In response to the input voltage signal and current transmitted between the buffers, the current mirrors produce currents that differ in proportion to the difference between the input and reference voltage signals. The current mirrors also reproduce the differing currents in output paths as the output current signals. A fixed current source is coupled to each output path for drawing a fixed current from each path to linearize the current difference.

Abstract: A system for correcting display distortion caused by CRT beam current changes in an oscilloscope system is disclosed. A Z-axis signal proportional to the CRT beam current is multiplied by two factors adjustable for either or both of X and Y axes and then added to the respective axis deflection signal which controls CRT beam deflection, thereby providing improved display quality.

Abstract: A serial DAC comprises two shift registers having their data input terminals connected together for receiving serial binary data. The shift registers are clocked alternately, whereby each shift register is clocked at substantially half the rate at which data is applied to the data input terminals of the shift registers. Two current switches are associated with the shift registers respectively, each switch being operative to steer input current to one of two output terminals if the data output of the associated shift register is a digital 1 and to steer input current to the other output terminal if the data output is a digital 0. Two current sources supply equal, constant currents to input terminals of the two current switches respectively.

Abstract: A junction field effect transistor circuit is used to detect the power level contained in radio frequency signals over a wide range of frequencies and signal levels. The radio frequency signal is coupled to the drain of a junction field effect transistor, the gate of which is biased at a d.c. potential equal to the pinch off voltage. The radio frequency signal is also coupled to the gate. The resulting current from the source contains a d.c. term proportional to the square of the magnitude of the radio frequency signal, as well as time varying signal components. A low pass filter is employed to remove the time varying signal components from the resulting source current to produce a D.C. output current which is proportional to the power level of the input signal.

Abstract: A trigger holdoff system particularly useful in digital oscilloscopes is provided in which a holdoff pulse is generated in response to a trigger pulse from a trigger generator and applied to the trigger generator to disable a time base control circuit.

Abstract: A digital oscilloscope provides sine interpolation between sampled data points and includes means for intensifying the cathode-ray-tube display to emphasize portions of the cathode-ray-tube trace corresponding to original samples while deemphasizing portions of the trace representing interpolated information.

Abstract: A rotary control having a variable detent is disclosed. The control, for electrical instruments and the like, includes a manually rotatable shaft to which a plate is coaxially mounted. The plate includes magnetizable flutes extending radially therefrom, each flute corresponding to a rotational stop position of the rotary control. Spaced adjacent the plate is a switchable electromagnet that forms a detent. A control switch in communication with the electromagnet selectably energizes it to engage magnetically the flutes successively as the shaft is manually rotated, stopping the rotary control at each rotational stop position. The switch also de-energizes the electromagnet so that the shaft may be continuously variable. A plurality of electromagnets can be positioned about a plate to vary the locations of the rotational stop positions. In a separate embodiment, a plurality of plates, each with an associated electromagnet, is mounted coaxially on the shaft.

Abstract: An oscillator produces an output signal which is frequency locked to a reference signal but phased locked to a triggering signal. The oscillator includes a NOR gate having its output fed back to one of its inputs through a programmable delay circuit while the triggering signal is applied to another of its inputs. When enabled by the triggering signal, the output signal of the NOR gate oscillates at a frequency inversely proportional to the delay time of the delay circuit. The delay time is controlled by a control circuit which counts NOR gate output signal cycles occurring during a predetermined number of reference signal cycles and increments the delay time when the count is higher than expected for an oscillator output signal of a desired frequency and decrements the delay time when the count is lower than expected.

Abstract: A device for controlling the output voltage range of a digital-to-analog (D/A) converter of the type wherein the converter output voltage range is proportional to the magnitude of an applied bias current. The device comprises means to sample and store a selected converter output voltage, means to produce a variable current of magnitude proportional to the stored converter output voltage, and a source of constant current. The constant current and the variable current are summed and applied to the converter as the bias current. The converter output voltage range is dependent on the variable portion of the applied bias current which is in turn dependent on the stored, selected converter output voltage.

Abstract: A method for digitally measuring waveforms is provided in which absolute and relative amplitudes and time information of electrical signals is electronically determined. A pair of cursors, which are operable in both independent and tracking modes, are used to provide alignment with reference points and selected measurement points so that the voltage difference between the cursors may be utilized by a digital voltmeter to provide the measurement data.

Abstract: A data storage element having input and output ports isolated from a regenerative latch portion so that the data transmission path is not through the latch. The circuit arrangement provided greatly reduces the probability of a metastable occurrence and permits data acquisition at a high rate with minimal error, and thus is suitable for use in high-speed digital shift registers.

Abstract: An apparatus for calibrating a timer of the type having a first and a second input channel in which an initial signal arriving over one input channel initiates a timing cycle, while a subsequent signal arriving over the other input channel terminates the timing cycle, the initial and subsequent signals being transported to remote ends of the first and second input channels from remote sources by means of first and second signal conductors. The apparatus comprises a commoning conductor, a test signal source, and first and second signal routing networks, the first signal routing network being capable of selectively coupling the first signal cable, the test signal source, one end of the commoning cable, and the first timer input channel, while the second signal routing network is capable of selectively coupling the second signal cable, the test signal source, or another end of the commoning cable and the second timer input channel.

Abstract: In accordance with the present invention, a control circuit for operating a delayed sweep oscilloscope includes a reversible counter which may be selectively incremented or decremented to establish a number of trigger-circuit operating functions and modes, such as trigger source selection, coupling, level, and sweep mode. A plurality of light sources behind a plastic overlay laminated to the front panel indicate the various functions and modes.

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 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 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 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 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.