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: 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.