Patent GB-672877-A (GB)
Title: Method and apparatus for producing a film record of a scene appearing on a television screen
IPC: H04N5/84
Filed: 1948-03-08
Abstract: 672,877. Television. RAIBOURN, P. March 8, 1948 [Oct. 7, 1947], No. 7121/48. Class 40 (iii). In a system for producing a record on cinema film of a television transmission wherein the cine-camera operates at 24 frames per second while the television-picture recurrence frequence is 30 c/s., the television signal is, by means synchronized by the received synchronizing signals, reproduced on the screen of a cathode-ray tube for successive periods of <SP>1</SP>/ 30  sec. separated by intervals of <SP>1</SP>/ 120  sec. during which the cathode-ray beam is switched off so that the cathode-ray tube screen may be photographed directly by the cine-camera to obtain a record which comprises one complete television picture per film frame. The motor for the cine-camera is driven by a locallygenerated 60 c/s. supply synchronized by the received synchronizing signals. In Fig. 1, the'received signals are applied to a conventional television receiver 11, the output of which is applied to a cathode-ray tube 12. The horizontal-synchronizing pulses are applied to circuit 14 which develops periodic blanking pulses which are applied to the cathode-ray tube 12 to suppress the reproduced picture during the intervals when the photographic film in the camera 13 is stepped on. The circuit 14 also develops a signal which is applied to 3-phase generator 31 which drives the synchronous motor 32 controlling the camera 13 in synchronism with the blanking of the cathode-ray tube 12. Detailed description. Circuit 14, Fig. 1, is illustrated in Fig. 2, the horizontal synchronizing pulses from the receiver I being applied to a gating circuit 15 and to a frequency divider 26, which delivers a 24 c/s. output pulse signal. Each component pulse of this signal is applied to a trigger circuit 25 of the flip-flop type which is switched thereby to a state which causes the gating circuit 15 to " open." Synchronizing pulses passing through the gate are applied to blocking oscillator 16 which is triggered by the first pulse applied thereto, and to a counter circuit 22 which delivers a pulse signal after 525 pulses have been applied thereto (i.e. after a complete television - picture interval has elapsed). The pulse from circuit 22 is applied to trigger circuit 25 which then reverts to its original state and " closes " the gating circuit 15. The outputs from blocking oscillator 16 and counter circuit 22 are applied to a flip-flop trigger circuit 17 which consequently generates a 24 c/s. square wave which is applied to the control grid of the cathode-ray tube to switch the cathode-ray beam on for the period of one television picture once during each <SP>1</SP>/ 24  sec. An output from the frequency-divider 26 which may conveniently be at 120 c/s., is taken to the circuit 31, Fig. 1, where, after shaping, it is applied to a frequency-dividing blocking oscillator which delivers a 60 c/s. output. The 60 c/s. pulse signal is converted to a saw-tooth waveform which is applied to a tuned circuit to give a sinusoidal waveform. This is then applied to three parallel circuits, two containing appropriate phase - shifting devices, which deliver, by means of thyratron relay circuits, a three-phase power supply for driving the motor 32. In an alternative arrangement the verticalsynchronizing pulses are used to derive the three-phase supply for the motor 32.