Abstract: Display of alphanumeric characters symbols, graphs and other information in a dot-matrix form on a CRT is enhanced by modulating the CRT beam sinusoidally at twice the dot matrix clock rate to produce two full cycles of sinusoidal modulation for each dot space. The amplitude of the modulation is selected to be one-fourth the raster scan spacing of the CRT, whereby two sinusoidal cycles of modulation in each dot space more fully fills the space allocated to a dot display in the vertical direction as the electrons beam scans the dot space in the horizontal direction.

Abstract: Chroma crawl, and a 15 Hz component introduced by the NTSC subcarrier pattern repeated every four fields, is obviated by adding to and substracting from the horizontal and vertical sync timing of alternate frames the period of one half cycle of the color subcarrier. Upon encoding television color signals with the color subcarrier for transmission in a compact video signal with the horizontal and vertical signals generated by this method, a chroma crawl free composite video signal results without producing any cumulative timing difference.

Abstract: An LC tank circuit in the collector of a power transistor controls the vertical modulation of the horizontal deflection of a CRT through additional deflection coils properly oriented. The tank circuit is tuned at a frequency nf for the desired modulation, where n is the number of cycles of oscillation of the tank for each drive pulse at a frequency (pulses per second) f, and each drive pulse is adjusted in width to one fourth or less of a cycle of the modulation frequency nf using an adjustable RC differentiating circuit and a threshold device to couple a squarewave signal at frequency f to the base of the power transistor.

Abstract: A three-pole double-throw switch is provided to selectively interrupt the video signal from an input connector to an output connector for display of white characters generated by a microprocessor on a dark screen of a CRT monitor, or vice versa, and route the video signal through an inverter for display of dark characters on white screen. One pole of the switch is used to provide the vertical sync signal to the power input terminal of the inverter, thus powering the select switch box solely from the transmitted vertical sync signal. A capacitor filters the power supply thus provided. The select switch box requires no external power and is virtually free of RF energy radiation while providing noise free data display with equal bandwidth response in both modes.