Patent GB-1026534-A (GB)
Title: Improvements in or relating to communication systems
IPC: H04N7/00
Filed: 1961-10-25
Abstract: 1,026,534. Television; radio-frequency systems. C. A. MORCHAND. Aug. 16, 1962 [Oct. 25, 1961], No. 38263/61. Headings H4F and H4L. [Also in Divisions B7, G1 and G5] A television system for educational purposes incorporates a main transmitter 10-1 transmitting a principle source of information, a number of additional transmitters, e.g. 10-N transmitting supplementary information or repetitions of part of the principal information, and a television receiver 14, for use by a pupil, which has a channel selector 18 which may be actuated by a solenoid 50, when a selected one of switches 44a-44n is closed, to cause reception from any desired transmitter, the arrangement being such that in addition to closing a switch 44a control signal must also be received from one of a group of photoelectric cells 40a-40n positioned to respond to a spot of light produced at one side of the television screen 42. In a typical method of use, the receiver is tuned to the main transmitter and at a critical or difficult stage in the transmitted information it is announced that supplementary or additional information is available from certain of the other transmitters. Thereupon, signals to produce spots of light at positions individual to the other transmitters are added to the transmission. If the pupil then closes the corresponding switch 44a- 44n, the solenoid 50 is pulsed and the receiver returned to the appropriate additional transmitter. For example, to switch to the first additional transmitters, switch 44a is closed and a single pulse of light is produced at the position occupied by photo-electric cell 40a. To switch to the second additional transmitter, switch 44b is closed and two pulses of light are produced at the position occupied by photoelectric cell 44b so that solenoid 50 is pulsed twice. At the completion of the additional or repeated information the receiver is controlled by appropriate switching and pulsing so as to retune to the main transmitter. At the transmitters, Fig. 2 (not shown), the signals to produce the spots of light are produced by an additional camera viewing a line of lamps which may be lighted as desired by switches operated manually or by a punch-tape device. The transmitted information may be " live " or may originate from film. The receiver has two additional photo-electric cells, the first 240 is independent of the viewing screen and operates when switch 244 is closed to permit the pupil to control the channel selector mechanism by flashing a light on to the cell; the second 140 responds to a spot of light on the viewing screen when switch 144 is closed to operate a unit 130 which may, for example, control the room lights. The educational facilities may share channels conveying normal programmes by arranging a conventional programme to occupy the top three-fifths of the viewing screen and the educational programme the remainder of the screen. A mask is provided for blocking either of the programmes from a viewer. An application of the system to a simulator for teaching driving of a vehicle is described (see Division B7).