Progress report on the development of a photo-electric beam-index colour-television tube and system

The paper is a progress report on the development of an index colour-television display using photo-electric indexing, and outlines some of the basic problems associated with index systems. The effect of cross-modulation between the writing and index signals is examined and a method of overcoming this cross-modulation is suggested. The effect of the delay around the index loop and its relationship with the horizontal time-base linearity is discussed, and a preferred circuit arrangement which relaxes the tolerances on this linearity is described. Some comparisons are drawn between index and other colour-television displays, and details are given of the practical verification of the system described. The present system may lead to a simplification of the colour display tube.