Patent GB-709922-A (GB)
Title: Improvements relating to indicating apparatus
Inventor: TAYLOR MAURICE KENYON
IPC: G08C15/00
Filed: 1951-03-06
Abstract: 709,922. Photo-electric control systems. FERRANTI, Ltd. May 19, 1952 [March 6 1951], No. 5353/51. Class 40 (3). [Also in Group XXXVIII] A plurality of conductors are adapted to be energized singly, and the conductor energized at any moment is indicated at a distance by sending coded signals representing the number of the conductor in a selected scale of notation of radix n. A plurality p of photo-cells, one for each power of the radix n, required to represent the highest conductor number are provided, and, associated with each " power " photo-cell, are one or more sets of n digit-representing-light modulating devices, the n devices in each set representing by different light modulating characteristics the n digits 0, 1 . . . (n-l) in the scale. Energization of any one conductor connects in series those digit devices associated with the various photo-cells corresponding to the number of the conductor, and the coded signals representative of the conductor are derived from the photo-cell outputs. Transmitter.-Fig. 1 shows a selector switch the fixed contacts 10 of which are numbered in the binary system 001 ... 111. Photo-electric cells 23<SP>0</SP>, 23<SP>1</SP>, 23<SP>2</SP> of the emissive type, corresponding to the powers 2‹, 2', 2' are associated respectively with electric lamps 13-16, 17-18, 19, and the various switch contacts 10 are series connected to a combination of the lamps 13-19 representing the associated binary numbers, so that when a contact 10 is selected e.g. that numbered 111, by the switch arm 11, corresponding digit lamps, in this case, the three lamps 13, 17, 19 are lighted to illuminate the corresponding photo-cells. from the output circuits 24<SP>0</SP>, 24', 24<SP>2</SP> of which signals are transmitted to line. Separate lamps may be provided for the combination appropriate to each number, Fig. 3 (not shown), and the light modulation effect may be produced, alternatively, by interposing, between a constant source of illumination and the cells, electrically controlled shutters, Fig. 4 (not shown), or Kerr cells. To avoid false transmission when the switch arm 11 bridges two contacts 10, the binary numbers may be allocated to the contacts in such a way that the binary numbers of adiacent studs differ in respect of one digit only, Fig. 5 (not shown). If zero digits are also to be transmitted, zero lamps 54, Fig. 6, are series connected between the appropriate switch contacts 10 and the lamps 13-19. These zero lamps are associated with photo-cells 52<SP>0</SP>, 52', 52<SP>2</SP> which, like the photo-cells 23<SP>0</SP>, 23<SP>1</SP>, 23<SP>2</SP> represent the powers 2<SP>0</SP>, 2', 2<SP>2</SP>, so that the zero signal is sent from the appropriate power output 53<SP>0</SP>-53<SP>2</SP>. The zero lamps may of course be replaced by electrically controlled shutters or light-valves (Kerr cells). alternatively, where digit lamps are used as in Fig. 1, both the zero and unit digit lamps may be associated with a single " power " photo-cell, Fig. 7, the zero lamps 60 emitting a different light intensity from the unit digit lamps 13-19, so that zero is distinguished from unity in the line by the signal amplitude. Zero and unity may alternatively be distinguished by using in lieu of lamps of different light intensity, light filters having different translucency factors. Fig. 8 shows a similar but ternary scale arrangement in which the digits 1, 2 are distinguished by lamps 70, 71 of different light intensities. Other scales may obviously be used by providing (n) lamps of different intensities or n filters of different translucencies, or (n-1) where zero is not to be transmitted, to modulate the photo-cell for each power n<SP>0</SP>, n<SP>1</SP> . . . nn' in n or (n-1) different ways as the case may be. Receiver.-Fig. 2 (not shown). This is as described in Specification 709,921, [Group XXXVIII]. Specifications 709,910 and 709,918, [both in Group XXXVIII], also are referred to.