Patent GB-465184-A (GB)
Title: Television transmission method
IPC: H04N5/073
Filed: 1935-08-06
Abstract: 465,184. Television. RADIOAKT.-GES. D. S. LOEWE. Aug. 6, 1935, No. 22115. Convention date, Sept. 4, 1934. [Classes 40 (iii) and 40 (v)] A film, scanned by a perforated disc 10, undergoes a mechanical or optical movement during the scanning of a picture to produce the displacement between sets of scanning- lines necessary for interlaced scanning. The film is moved upwards below a double-spiralled disc, Fig. 2, and each spiral is made operative in turn by a shutter 64. Framing signals are produced by a shutter 65. The Specification as open to inspection under Sect. 91 comprises also the following subject-matter. At the end of each rotation of the disc the image 10<1> of the film, Fig. 3 (Cancelled), is shifted by the width of one scanning-line by a rocking of a glass plate 16 between stops 18, 19. The area of the image is lit by auxiliary light 21 to ensure a sufficient synchronizing signal when the apertures pass over the darkened edge. When the film 6, Fig. 2b (Cancelled), is moved continuously, the scanning lines produced by a disc 10 are moved in the opposite direction by a mirror drum 9, and the change from one partial scan to the next occurs on the passage from mirror to mirror. The framing signal may be produced by omitting some apertures, Fig. 11 (not shown), or by a darkened horizontal edge. Since the signal is started by the previous aperture passing over the black edge, the framing signals start in exactly the same way as the line-synchronizing signals. The image may be projected on an iconoscope screen with two darkened lines to produce the framing signal, Fig. 17 (Cancelled) (not shown). Cathode-ray scanning, Fig. 6 (Cancelled). When a long framing signal is sent at the end of each complete scan, the displacement between successive sets of lines is produced by a special gas-discharge triode 45. Short quenching impulses are applied to the anode at the end of each partial scan from a vertical deflecting-plate 53. The longer framing impulses applied to the grid overcome these and cause the tube to conduct until the quenching at the end of the first partial scan. The potential developed by the discharge current through a resistance 59 produces the relative displacement of the sets of lines. When there is an unequal number of lines in each partial scan, the framing signals are generated by a rotating disc with two projections intersecting a beam of light, and each of them is off-set with respect to the diameter passing through the other, Fig. 15 (Cancelled) (not shown). When a framing signal is sent only at the end of each complete scan, the circuit shown in Fig. 16 (Cancelled) is used at the receiver. Impulses from the horizontal deflecting plates 95, 101 are applied to the grid of a gas-discharge tube 81 through a circuit 97, 98 and framing-signals are superimposed from a lead 92. When the framing signal is present, the tube discharges one line earlier, or later, than when it is absent. The tube discharges through a resistance 82 of sufficient value to make the discharge last for the period of at least one scanning-line. Amplifiers. The very low frequency components are amplified in a separate resistance-coupled amplifier fed from a potentiometer in the form of a gas-discharge path, Fig. 5 (Cancelled) (not shown). Alternatively the detector of a superheterodyne receiver is coupled directly to the controlling element of the cathode-ray tube, Fig. 8 (Cancelled) (not shown). This subject-matter does not appear in the Specification as accepted.