GB845440A - Improvements in or relating to monitors for use in television equipment - Google Patents

Abstract

845,440. Television. RANK CINTEL Ltd. Feb. 18, 1958 [Feb. 18, 1957], No. 5474/57. Class 40(3). Television monitoring apparatus comprises a single cathode-ray picture tube on which two pictures corresponding to two television signals derived from separate sources are displayed, effectively, simultaneously on non-overlapping areas. This is achieved by effecting the scanning in one of the two co-ordinate directions at one half the normal frequency and supplying the two sets of signals sequentially to the tube of half the frame frequency Fig. 1, shows the display produced (the two sets of signals corresponding, e.g. to a circle and a square), when the line scan frequency is reduced to one half and Fig. 2, that produced by reducing the frame scan frequency to one half. The altered aspect ratio of these two displays may be partly corrected by viewing them through a large cylindrical lens. To produce the normal 3:4 aspect ratio of the Fig. 1, display the amplitude of the line timebase is increased and that of the frame timebase reduced resulting in the display of Fig. 3, whilst reducing the amplitude of the line timebase and increasing that of the frame timebase allows the display of Fig. 2 to be altered to that shown in Fig. 4. A block circuit arrangement which allows either a single picture of maximum size and normal aspect ratio or any of the two displays described above to be produced is described with reference to Fig. 5 (not shown).