| 摘要 |
330,220. Baird, J. L., Television, Ltd., and Baird Television, Ltd. Jan. 31, 1929. Divided on 328,616 and addition to 291,127.. Television.-A receiving screen contains a substance whose colour is changed under the influence of the signals, the change being subsequently reversed (so as to obliterate the picture) in readiness for the succeeding signals. Thus (a) a screen treated with gum guaiacum may be scanned (Fig. 1, not shown) with blue light, which darkens the gum, and then exposed to red light which obliterates the effect of the blue. This result may be achieved by means of a scanning disc similar to that described in the parent Specification. The scanning and obliterating light-sources may be arcs with blue and red colour-screens respectively, or a single lamp may be associated with a suitably arranged mirror and colour-screens, or the scanning apertures may be covered with blue screens while an obliterating aperture is covered with a red screen. (b) In the arrangement shown in Fig. 3, a screen 16 of paper treated with potassium ferrocyanide, or other " pole-finding " substance, is scanned by brushes 12 to which negative signal currents are applied so as to produce a change of colour by electrolytic action. The picture is periodically obliterated by the positive brush 14. Suitable circuit arrangements are described in the Specification (Fig. 2, not shown). |
