Patent GB-906591-A (GB)
Abstract: 906,591. Television. PHILIPS ELECTRICAL INDUSTRIES Ltd. Sept. 30, 1958 [Oct. 2, 1957], No. 31236/58. Class 40 (3). [Also in Groups XXXVI and XL (a)] In a circuit arrangement for converting time signals into position signals by means of a delay network, the tappings on the delay network are connected to individual electrodes on one side of a strip of material which as a set of corresponding electrodes on the other side, the strip being capable of being rendered momentarily conductive and such that conductance between successive pairs of electrodes steadily increases to compensate for attenuation along the delay network. Fig. 1 shows a suitable strip comprising a region 1 of a first photo-conductive material and a region 2 of a different photoconductive material so that the conductance between successive pairs of opposite electrodes 9 increases along the length. The same effect may be achieved by a strip of homogeneous material as shown in Fig. 3a, in which the distance between successive pairs of electrodes steadily decreases to provide the increasing conductance. Such arrangements may be combined to give increasing conductance in both the x and y directions. An electro-fluorescent material of zinc sulphide, activated by manganese or manganous chloride, may be associated with the photo-conductive strip to provide a light image corresponding to the input signals and this arrangement may be adapted for television signals. A further arrangement suitable for television is shown in Fig. 6 in which n arrangements, each comprising a delay circuit 4 and fluorescent layer 5 connected on either side of a strip such as that of Fig. 1, are provided, and the thickness of the strip 1, 2 decreasing towards the nth arrangement. Thus, television signals may be supplied from source 3, each arrangement corresponding to a line, and the n arrangements constituting the frame; when the desired voltage pattern is complete momentary radiation 7 is applied at appropriate instants to render the layer conducting to cause the strips 5 to emit light. Fig. 9 shows a further modification in which a PN rectifying layer 12 is used to provide the momentary conduction (by means of an applied forward biasing impulse) instead of a photo-conductive layer. Metal islands 9 connect the rectifying layer to delay circuit 4 and to fluorescent layer 5 which is covered by a transparent electrode 6 to which the forward biasing impulse is applied. The lower portion consists of a transparent electrode 9 covering metal islands 9 on a photoconductive strip such as that of Fig. 1 with tappings b 1 -b n  which may be connected to a television panel. The conductivity of the rectifying layer 12 may be raised along its length by providing a variable thickness layer of carbon. The photo-conductive layer may be produced by mixing powders or depositions of two materials in different proportions or by having a varying proportion of an insulating binder material or of activators or de-activators. CdS with varying proportions of Cu and or Hg is specified. Amplifiers may be used in conjunction with the varying conductivity layer to increase the effect and the delay circuit may be electrical or electro-acoustical.