Abstract: A correction circuit is used with a horizontal deflection circuit, for the correction of an image distortion. The correction circuit comprises a line memory for sequentially fetching and storing one-field digital image data. The digital image data read out of the line memory is supplied to a D/A conversion circuit. This D/A conversion circuit converts the digital image data into an analog signal used for making a beam scan rate constant on the entire screen of a CRT. The data transfer rate used in both the line memory and the D/A conversion circuit is varied, with a clock supply rate adjusted by a frequency modulation circuit and an A/D conversion circuit on the basis of clock rate data.

Abstract: A picture display device includes a generator for generating a periodical staircase-shaped signal for addressing picture elements on display screen. The initial value of the staircase shape is settable and a stepwise change takes place each time upon the occurrence of clock pulses. The height of the steps is determined by the following measures:measuring the value of the staircase shape at a predetermined measuring instant or measuring the instant when the staircase shape is at a predetermined level,comparing the measured quantity with a predetermined target value,deriving a new value from this comparison and from the set initial value for the height of the steps of the staircase shape, for which new value the difference between the measured quantity and the target value has a predetermined value, andsetting the height of the steps of the staircase shape at this new value.

Abstract: A raster deflection signal generator that generates deflection signals in accordance with sweep control signals provided by a programmable timing generator. The programmable timing generator stores digital signals representative of the desired sweep control signals so as to tailor the sweep timing to the input video channel. The digital sweep control signals are synchronized to the input video channel by locking a horizontal sync pulse generated by the programmable timimg generator to the horizontal sync pulse of the video input channel by a phase locked loop. Each deflection sweep is compared to a threshold voltage representative of screen center to provide a duty cycle signal in accordance with drift of the TV image from screen center. The duty cycle signal is filtered and sampled and fed back to the sweep generator so as to maintain the deflection sweeps properly centered.

Abstract: A digital conversion circuit with a convergence deviation correcting circuit. A coefficient storing circuit stores coefficients of fundamental correction waves. By weighting these fundamental correction waves using the coefficient storing circuit, a correction data storing circuit is provided with correcting data. Controlling means controls this entire operation. Using the correction data, the convergent deviation of a scanning line of a scanning picture is corrected. By weighting each fundamental correction wave with a weighting coefficient, a synthesized wave is produced. This synthesized correction data is read from a correction data storing circuit in synchronism with deflection scanning and is supplied to a convergence deviation correcting circuit.

Abstract: A delay time between the start of a trace on an oscilloscope screen and a point along the trace is computed based on measured "sweep gain" and "sweep start" parameters characterizing a triggered sweep signal controlling the horizontal position of an electron beam creating the trace, the sweep signal increasing when triggered from a starting level at a constant slew rate to move the beam at a constant speed across the screen. The sweep start parameter is the value of input data applied to a digital-to-analog converter (DAC) which would cause the DAC to produce an output voltage equal to the sweep signal starting level, and the sweep gain indicates the rate of increase in DAC input data required to produce a DAC output signal with a rate of increase similar to the slew rate of the sweep signal. The horizontal position of the point along the trace is the beam position on the screen at the moment the sweep signal magnitude reaches the magnitude of the DAC output signal.

Abstract: The oscilloscope sweeping circuit includes a first D/A converter which converts sweep rate step digital data into a charge current under the weighting of a reference current applied thereto. The charge current charges a capacitor and the amount of the charge determines the sweep rate. The reference current is produced by a second D/A converter which converts fine step digital data into an analog current.

Abstract: A digital bandpass oscilloscope permits an operator to observe both time and frequency domain plots of analog signal components of frequency within a passband of selected center frequency during a time window of selected duration. The input signal is digitized, and the resulting digital data sequence is bandpass filtered and decimated by an adjustable decimation ratio to produce stored waveform data indicating the time dependent behavior of the passband during the time window. The oscilloscope, which utilizes the waveform data to produce both time and frequency domain displays of the passband, adjusts the decimation ratio to ensure that the number of data elements in the waveform data sequence is constant regardless of the selected duration of the time window and adjusts the bandwidth of the passband to minimize aliasing in the time domain display.

Abstract: A memory control for use with a digital oscilloscope having a display and a digital memory storing a sequence of signal samples. The sequence of signal samples is cyclically read from memory and displayed. The memory control adjusts the memory access operation to provide a controlled signal flow to the display at a rate within the slew-rate limits of the graphic display. In the memory control, the point slew, or distance over which the display beam moves from the present data point to the next point, is measured. If the point slew relative to the time interval between displayed signal samples exceeds the slew-rate capability of the display, the signal flow from the memory for subsequent data points is reduced or inhibited for a time sufficient to allow the display to reach a coordinate position corresponding to the desired data point.

Abstract: Horizontal and vertical deflection windings in a deflection yoke coil assembly of a CRT (cathode ray tube) having stroke written or raster scan displays are driven by x and y analog deflection signals, respectively. Each of the x and y analog deflection signals are converted to x and y digital signals, respectively, sampled to provide x, y sample sets which are coupled to a digital x correction signal memory and a digital y correction signal memory, respectively. Geometric corrections are stored in the memories for each of a predetermined number of x, y signal set values which correspond, respectively, to a number of point locations over the CRT screen. The x and y corrections that are addressed from the memories are supplied to MDACs (multiplying digital to analog converters) and then to analog delay line filters which supply the x, y analog correction signals for summing with the x, y analog deflection signals, respectively.

Abstract: A multiplying digital to analog converter using ladder networks and binary weighted load compensation to allow integration and video frequency operation. In one form, the circuit is configured from field effect transistors which incorporate by virtue of their structural and operational characteristics both the switching and resistive functions of R-2R ladder networks. The circuit is used to convert digital format words representing intensity and color (red, green and blue) into analog red, green and blue display drive signals. According to that configuration, the output of the digital to analog intensity word converter serves as the reference for the three digital to analog color word converters. Loading effects attributable to differences in the bit content of the color words are offset by a binary weighted switched load which is responsive to a digital compensation word. The switched load is also connected to the output of the intensity word converter.

Abstract: A digital storage oscilloscope comprises an analog-to-digital converter for receiving an analog input signal and generating a succession of data words representative of the instantaneous magnitude of the input signal at a succession of equally-spaced sample times. A waveform memory has a plurality of separately addressable storage locations for storing the succession of data words at locations of which the addresses are related to the respective sample times. A trigger circuit compares the instantaneous magnitude of the analog input signal with a predetermined trigger level and generates a trigger pulse when the instantaneous magnitude of the input signal bears a predetermined relationship to the trigger level. The trigger circuit also causes an address word to be stored that defines the storage location for the first data word that occurs after the trigger pulse.

Abstract: A CRT display system providing a raster pattern, possibly for a flat screen CRT, has an oscillator driving a Line counter. The Line counter drives a Field counter and a Line DAC. The Field counter drives a Field DAC. In response, there are generated signals, representing functions, to be applied to the CRT deflection plates, and whereby there is represented the inverse of any function representing distortion of the raster pattern required to be corrected. At least one further DAC may be provided, comprising one of a pair of interacting DAC's, with one DAC driven by the Line counter, and one DAC driven by the Field counter, the output of said further DAC causing a combined function to be represented by the output of said other DAC. Said other DAC may comprise either the Line DAC, or the Field DAC; or said further DAC of another pair of interacting DAC's.

Abstract: Digital apparatus for convergence correction of a plurality of images on the screen of a television monitor includes a digital registration circuit, or an analog registration circuit using a digital attenuator; and a memory for storing data for operation of the digital registration circuit or the digital attenuator of the analog registration circuit. The memory has a plurality of pages, and the correction data corresponding to different operating conditions is stored in the respective pages of the memory. The paging of this memory is performed in accordance with the operating conditions, and the convergence correction is carried out on the basis of the correction data continuously read out of the designated page. With this apparatus, accurate convergence adjustment can be simply performed to accommodate changes in size and/or shape of the image displayed on the screen or monitor, changes in the distance of a projection screen from its projector, and changes in the screen surface, i.e.

Abstract: An instrument for providing a principal display representing the variation of a first quantity as a function of a second quantity, comprises a display screen. A visually distinct dot is generated on the display screen and is deflected along one of two orthogonal axes in dependence upon the value of the first quantity and along the other axis in dependence upon the value of the second quantity. The dot is additionally deflected to selected positions along the two axes to generate an auxiliary display of a marker and of an information-conveying character adjacent the marker. The position of the auxiliary display is adjustable along at least one of the axes.

Abstract: A digital-to-analog converter comprises a current source for supplying a current of predetermined magnitude to a circuit node, and a switch connected to the circuit node, and defining a first current path leading to a reference potential terminal and a second current path leading to an output terminal. The switch has an input terminal, at which it receives a first digital signal of one binary digit for conversion to analog form, and also has a reference terminal, and has a first condition, when the voltage at the reference terminal is higher than that at the input terminal, in which the current supplied to the circuit node is delivered to the output terminal, and a second condition, when the voltage at the reference terminal is lower than that at the input terminal, in which the current is delivered to the reference potential terminal.

Abstract: In a graphic display apparatus having a digital differential analyzer (DDA), a chrominance data stored in a register is written in an area of a bit map memory defined by coordinates generated from DDA by a write control circuit in response to ARDY signal. A first flip-flop is reset by a busy signal from the write control circuit and is set by a load signal. When the first flip-flop is in a reset state, a first gate produces PRDY signal requesting a microprocessor to load the chrominance data in the register in response to RDY signal indicating completion of a coordinate setting operation from DDA. When the first flip-flop is in a set state, a second gate generates CRDY signal in response to RDY signal. CRDY and RDY signals are supplied to a selector which selects one of them due to a second flip-flop for switching a line processing mode and a raster operation mode, and supplies the selected signal to the write control circuit to thereby perform write operation.

Abstract: A CRT display system providing a raster pattern has digital means 30, 31, 32 to drive a DAC 34. In response, there are supplied analogue signals, on a line 37. There are also provided pulse generating means 90 controlled by the digital means, and integrating means comprising two integrators. Each integrator is connected individually to an X deflection plate 14 of the CRT, and comprises an amplifier and a feedback capacitor. One capacitor C2 is charged by negative-going pulses, and the other capacitor C2' is charged by positive-going pulses, until the pulses are removed, when the required ramps are applied to the deflection plates. Then a current flows through a transistor T7, and is controlled by the DAC output on the line 37. Hence, the waveforms applied to the deflection plates cause distortion of the raster pattern otherwise obtained, to be corrected, the DAC output representing a function comprising the inverse of the function representing the distortion.

Abstract: A color video monitor is disclosed which includes improved digital convergence using a plurality of memory means in which vertical convergence correction values are stored, one memory each for red, green, blue and lateral blue convergence values. Interpolation means provide additional values between the points stored in memory such that a smooth transition between successive lines of the display is achieved. The correction values stored in the memories are generated by means of a high-order polynomial function.

Abstract: Vector (i.e., line) drawings represent the "intelligence" content of images.A method is disclosed for the gathering of intelligence and the generation of vectors on the screen of a CRT without the usual problems associated with cost and performance.The Vector Generator itself uses pairs of digital-to-analog converters with a common analog output. This technique is referred to as interpolation. Careful shaping of the complementary reference voltages of the digital-to-analog converters results in constant velocity, transient-free vectors with starting and end points that are accurately controlled. Cumulative (i.e., closure) errors are entirely absent.

Abstract: In a digital wave observation apparatus having an A/D converter for A/D converting an input signal, a trigger level setting device for setting a trigger level, a trigger signal generator for comparing the input signal with a set trigger level and generating a trigger signal, a wave memory for storing an A/D converted input signal in response to the trigger signal, and a display for displaying the input signal stored in the wave memory, the apparatus has a trigger level display device for displaying a horizontal line corresponding to a trigger level on the display irrespective of generation of the trigger signal.

Abstract: A digital electron optics correction circuit for correcting the focus and astigmatism in a displayed image on a CRT is disclosed. The circuit includes a clock generator for generating a selected number of pulses between each horizontal blanking synchronization pulse. These clock pulses are then counted by an X-address counter and a first address signal is generated corresponding to a particular horizontal position on the CRT screen for each count of the X-address counter. A pulse generator circuit is also provided which is coupled to receive the vertical blanking synchronization pulses and which provides a selected number of output pulses for each vertical blanking synchronization pulse. A Y-address counter counts the output pulses from the pulse generator circuit and provides a second address signal corresponding to a particular vertical position on the CRT screen for each count.

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 circuit for converting a TV receiver to operate in accordance with the system associated with received signals, there being either F or F' scan lines in a field, with F<F', includes a counter driven by pulses each representative of one end of a raster scan line, and having M stages, with F and F'<M<2F and 2F'. There is also means to preload the counter selectively with a count of R or R', where (M-2R)=F and (M-2R')=F'. Wide window means detects when a field sync pulse is within a window including the (M-R)th and (M-R') stages, and, in response, the counter, initially, is preloaded with R'. Decision logic means then detects whether a field sync pulse occurs after the Kth stage, with K=M-[R+R']/2, when R' is continued to be preload; or occurs before the Kth stage, when R subsequently is preloaded; and the required TV receiver conversion is completed.

Abstract: A hybrid CRT display includes vector generated portions for alpha-numeric data and normal raster scan portions for symbol data. A deflection yoke for a CRT is driven by a single horizontal amplifier having switching means which operate the amplifier in three modes necessary to achieve the hybrid display, enhanced by resonant retrace during raster scanning.

Abstract: In a sampling digital oscilloscope means operable to measure the time period from the occurrence of a trigger signal to the onset of signal sampling period so that commulatively stored samples of a repetitively sampled signal visually coincide, producing a clear, jitter-free signal image. Moreover, the trigger signal is also produced according to a hold-off mode to allow the user to evaluate the results of processing the sampled signals by the digital oscilloscope before adding new data samples. In addition, a triggered update of stored data by new signals is provided, which is further controllable via an arm/disarm control to interrupt realtime updating of signals, allowing the user to observe signal changes as they occur.

Abstract: A digital video display system wherein the various characters to be displayed are displayed in the form of images of the complete character rather than the standard dot-matrix pattern of the prior art. A character generator in the display system stores signals representing the various characters to be displayed which are retrieved from storage in response to a character code. The signals are in the form of a binary code having a sufficient number of bits to represent a different number of levels of gray-scale or luminance values for the various picture elements making up the character image. The binary codes thus retrieved from storage are supplied to a video synthesizer that generates the video signal to display the character images which may be displayed in a number of different modes including white-on-black, black-on-white, black-on-gray, and white-on-gray as well as different combinations of such modes to represent a cursor.

Abstract: A waveform acquisition apparatus and method permits a plurality of samples of an input signal to be taken for each trigger recognition event, and stored at predetermined memory addresses to provide a complete equivalent-time waveform in which all accumulated samples are in correct time relation to each other. The mathematical determination of each address is obtained by measuring the time difference between a trigger recognition event on each cycle of a repetitive signal and a next occurring sample clock following each trigger recognition event, and then using a microprocessor to compute the relative addresses.

Abstract: The horizontal-deflection pulses (HA) and the vertical synchronizing pulses (VS) are applied to the count input (Ez) and the reset input (Er) of an upcounter (VZ) whose count outputs are connected to the address inputs (Ea) of a programmable read-only memory (PROM1) via a decoder (DC). The S-shaped characteristic of the deflection-stage current is approximated by portions of constant slope whose associated slope values are stored in the programmable read-only memory (PROM1) under one address each.

Abstract: A Digital Automatic Gain Control for a display system having a video display driven by a remote display generator including a display processor which generates binary words that are converted by multiplying digital-to-analog converters to analog deflection voltages that are applied to the video display. The deflection voltages applied to the display are sensed and a digital feedback signal is derived therefrom that is returned to the display generator. The digital feedback signal has a word size larger than the word size of the binary words generated by the display processor. The feedback signal is processed and applied to multiplying digital-to-analog converters and output amplifiers to modify the conversion from binary words to analog deflection voltages to thereby accomplish higher display resolution and accuracy than can be achieved by the display processor alone due to limited binary word size.

Abstract: Cathode ray tube drive circuitry in which non-linearity of the line scan is corrected by varying the frequency of the pel clock oscillator in accordance with anticipated variations in scanning speed. Predetermined speed corrections are stored in a digital store 23 and, by means of digital to analog converter 24 and integrator 25, are applied to the control input of a voltage controlled oscillator 13. Synchronization of the pel clock with the X-deflection waveform is effected by means of a parallel phase-locked loop comprising counter 15, sample and hold 18, amplifier 20 and low pass filter 21. Preferably a sinusoidal waveform is applied to the X-deflection coil in such a manner as to have a bidirectional raster scan, the X-deflection coil forming part of a tuned circuit of the sinusoidal waveform generator.

Abstract: A deflection circuit is disclosed wherein squarewave clock pulses are applied to the input of an n-stage shift register, the series input of which is connected to a fixed potential, the decoder is a summing circuit having n inputs each of which is connected to a respective output of the n-stages of the shift register, the resetting input of the shift register is controlled by the last shift register stage and a deflecting means is controlled by a sawtooth signal resulting at the output of the summing circuit.

Abstract: Non-linearities of an electron beam in a cathode ray tube are corrected in accordance with the position of the beam by circuitry which completes the correction from stored digital values. In response to positional signals X and Y, correction waveforms are generated in analog circuits 8H, 8V and 10. The waveforms are scaled by circuits 11 in accordance with the stored digital values and are summed in circuits 9R to 9L and applied to the windings of the cathode ray tube. Preferably the invention is applied to the correction of misconvergence in a shadow mask color tube.

Abstract: A novel circuit employing a differential integrator having differential inputs V.sub.1 and V.sub.2 provides a substantially uniformly varying output voltage representative of a straight line for connecting two display points having voltage levels V.sub.1 and V.sub.2. This circuit is ideally used in the reconstruction of analog waveforms from digitally stored data for display on an oscilloscope.

Abstract: A multilevel video display control circuit. A plurality of current levels are developed in response to coded command signals (P1, P2, P3). The generated currents are summed together and converted to analog voltage signals (V25) to control the brightness of the pixels on the display. A contrast adjustment network (26) includes a first potentiometer (K1) for setting the magnitude of one of the currents at a desired level. A second potentiometer (K2) is provided for varying the magnitudes of the other current levels while maintaining the first current at the preset magnitude. Preferably, the magnitude of the first current is inversely varied with respect to other current levels.

Abstract: A digitally controlled, presettable, ramp signal generating arrangement comprising digital to analogue converter means (DA) and integrator means (A1, A2) having a first mode in which its output (0) assumes a value representative of the output of the converter means, and a second mode in which its output changes at a rate dependent on the output of the converter means. The arrangement finds especial application in symbol display arrangements.

Abstract: Aberrations of an electron beam are corrected as the beam is scanned across the screen of a cathode ray tube by deriving correction signals from stored digital values by means of the calculus of finite differences. The digital values, which are the initial differences of polynomial correction functions, are held in store 10 and summed in adder 20, the results being converted by digital-to-analog converter 50 to analog signals and supplied to the cathode ray tube. Provision is made for the reduction of error in the calculations by shifting higher order differences relative to lower order differences before addition. The circuitry may be implemented on a single chip. Preferably, the invention is applied to the correction of misconvergence in a shadow mask tube.

Abstract: A digital oscilloscope is provided with a position control circuit which permits positioning of a signal both before and after digitizing. A track and hold circuit is coupled to the position control potentiometer to generate a reference voltage which tracks the position voltage in a waveform acquisition mode, and which is held at a fixed level in a display mode while the position voltage, which is applied to the acquisition preamp, is variable adjustable. A summation circuit subtracts the reference voltage from the position voltage to provide an altered positioning voltage for the display amplifier which is zero in the acquisition mode and variable in the display mode.

Abstract: The minimum output level of an electron gun driven at discrete voltage levels is precisely established. A target value slightly above the minimum voltage level is compared with the actual value. The result of the comparison is used to uniformily establish the minimum electron gun drive voltage and thus compensates for electron gun transfer characteristic differences and variations within the gun drive circuitry. An additional circuit utilizing a target value slightly below the maximum voltage can be used to establish the maximum output level of the electron gun.

Abstract: A sweep generator for producing a circular raster of curved scanning lines on the target surface of a video camera is disclosed. Each curved trace follows a substantially circular path through a scanning angle of 360.degree.. The circular raster is generated by horizontal and vertical scanning signals which are synchronized with the horizontal line frequency of a video receiver. The horizontal scanning signal is characterized by a constant amplitude component followed by a sine wave component, and the vertical scanning signal is characterized by a composite waveform including a constant amplitude component followed by a sine wave component which is shifted 90.degree. in phase with respect to the sine wave of the horizontal scanning signal.

Abstract: An electron source section including a first detecting sub-section and a first control sub-section and an image formation section including a second detecting sub-section and a second control sub-section are arranged in series. The first detecting sub-section detects at least one of the shape, diameter, brightness and spatial position of a crossover image formed by the electron source section to become an electron source of the image formation section and the direction of emission of the electron beam emitted from such crossover image, thereby to control the first control sub-section. The second detecting sub-section detects at least one of the shape and size of an electron beam image formed on a subject to be irradiated by the beam, and the current of the electron beam forming the electron beam image, thereby to control the second control sub-section.

Abstract: A cursive writing type cathode ray tube (CRT) display system in which the vertical size of the characters are increased by an input command from a keyboard and central processing unit (CPU). The CRT has both electrostatic and magnetic deflection systems with the magnetic deflection producing a raster in which each horizontal scan is electrostatically deflected to write characters on the screen. The characters are formed from stored digital codes selected by commands from the CPU. Digital to analog (D/A) converters produce analog deflection signals to produce a set of multiple strokes to form a character and to produce analog voltages for controlling the brightness of the stroke. Digital commands from the CPU are generated to increase or decrease the magnitudes of the various analog signals from the D/A converters when changing the vertical character size.

Abstract: An automatic Y-axis offset system for a cathode ray tube, which performs automatic positioning of a trace to a predetermined position on the cathode ray tube face such that the trace becomes visible, by applying a Y-axis offset voltage to the input signal voltage. The automatic positioning is performed when commanded by an operator through switch actuation. The offset voltage is produced by a feedback circuit which includes an amplifier receiving the input signal, a comparator for comparing an output voltage from the amplifier with a predetermined level, a counter which is enabled to count a clock signal so long as the level of output signal from the amplifier is different from the predetermined level, and a digital-to-analog converter which converts the count in the counter to an analog signal constituting the Y-axis offset voltage.

Abstract: A waveform acquisition circuit for both real-time and equivalent-time acquisition modes with a smooth transition between modes. The circuit includes a control circuit which causes an analog-to-digital converter to take samples of an analog waveform in precise time relationship with preselected data points along the time axis of the waveform. The data points may be preselected in accordance with a variable increment.

Abstract: A digitally controlled CRT display system providing display intensity levels having equal ratios of luminances for consecutive steps over a plurality of brightness control settings. The digital video is added to a digital brightness code and the sum is converted to an analog signal that is coupled to the cathode of the CRT. The digital-to-analog converter provides a transfer characteristic such that the consecutive gray shade steps have a constant ratio of luminance.

Abstract: Jitter due to sample uncertainty in a digital oscilloscope is reduced by horizontally shifting each frame of a repetitive waveform display to provide an apparent time coincidence of each frame. The time interval between a fixed point on the successive waveforms and the next succeeding clock edge is measured, and a correction voltage is produced to offset the sweep voltage by the corrected amount.

Abstract: A waveform observing method and apparatus incorporating signal sampling and digital technologies is disclosed. An input signal to be observed is compared with the output from a digital-to-analog converter and the comparison output is used for controlling display means such as a cathode-ray tube. A wideband input signal can be measured with much higher accuracy than the conventional apparatus.

Abstract: A general-purpose oscilloscope system is disclosed wherein waveforms acquired by the vertical and horizontal preamplifier channels can be displayed immediately, or they can be digitized and stored in a memory from where they can be recalled, reconstituted in their analog form and displayed at a later time. The processing system permits simultaneous display of instantaneous and processed waveforms, and includes facilities for processing associated z-axis signals and readout data as well. Access to peripheral equipment, such as a computer or the like, permits the digitized waveforms to be mathematically manipulated and returned to the memory in the processing system for ultimate display. The oscilloscope system can be assembled in a modular manner, whereby the processing unit becomes an integral part of the instrument, or the system can be assembled as a general-purpose oscilloscope without the processing unit, allowing a user to add the processing capability to his system at a later time.

Abstract: The invention is a method and structure for generating representations of repetitive electrical waveforms by sampling the magnitude of a plurality of points on the waveform. The sampling method is characterized by progressively forming an approximation of the magnitude of each waveform point during a plurality of repetitions of the waveform. In accordance with one feature of an illustrative embodiment of the invention, the magnitude of the waveform at each of the points is formed by successively comparing during a plurality of repetitions of the waveform the waveform magnitude to the magnitude of a reference signal associated with the point and by adjusting the magnitude of the reference signal after each comparison in accordance with the result of comparison. The invention includes circuit structure for performing the foregoing method.

Abstract: A three color gun cathode ray tube has convergence correction signals derived from digital signals stored in a digital data store. The screen of the tube is divided into a plurality of areas and a digital correction signal derived for each area. The system is arranged so that when the three beams are scanning a particular area the digital correction signal associated with that area is read out from the digital store, passed through a digital to analog converter and then applied to the convergence coils of the tube.

Abstract: A stroke writing generator develops selectively incremented and/or decremented horizontal and vertical deflection signals which simultaneously deflect all color associated beams of a conventional shadow-mask multi-color cathode ray tube to cause the beams to trace out a selected symbology on the tube screen. A video color code generator, operating in clock-defined synchronism with the stroke writing generator, selectively effects turn-on permutations of plural video amplifiers driving associated electron beams in the cathode ray tube to facilitate preprogrammed color tinting of the displayed symbology.