GB269834A - Improvements in or relating to television or like systems and apparatus - Google Patents

Abstract

269,834. Baird, J. L. Oct. 21, 1925. Television; synchronous movements. - Synchronism is maintained in a television system by the use at the receiving station of an image transmitted or controlled from the transmitting apparatus, such image being separate and of markedly different intensity from the picture being transmitted. In one receiving arrangement, Fig. 1, there is produced along one edge of the reproduced picture 11 a highly illuminated band 12 corresponding to a luminous object such as a lamp filament at the transmitting station, and during synchronous running the band 12 is disposed between light-sensitive cells 13, 14. Any divergence from synchronism produces movement of the band to activate one cell or the other according to the direction of the divergence, and the resulting current is employed to act upon an amplifying and controlling device 15 or 16 to accelerate or retard the receiving apparatus 17. In another arrangement, Fig. 2, a lamp 20, flashed intermittently under the con. trol of a periodic synchronizing impulse from the transmitting apparatus, co-operates with radial slots in a disc 22 driven from the receiving apparatus to produce on a screen 24 a band of illumination 25 coacting with two light-sensitive cells 26, 27. Alternatively the disc 22 may be replaced by a rotating mirror. The distance between the cells 13 and 14 or 26 and 27 may be adjusted. The two cells may be replaced by a single cell positioned so that half of its area from one edge is illuminated during synchronous running.