GB654439A - Improvements in or relating to receiving devices for image transmission - Google Patents

Abstract

654,439. Copying-telegraphy. PHILIPS ELECTRICAL, Ltd. April 29, 1948, No. 11770. Convention date, May 2, 1947. [Class 40 (iii)] In an arrangement for recording received picture signals on a moving film a device is provided for indicating, by means of a mark on the film, the beginning or end of each complete picture, the device being controlled by a signal which is transmitted during the interval between two successive picture transmissions. The film 21 which is drawn from a supply roll 22 by means of rollers 24, 25 driven by motor M via the transmission system including the elements 33, 36, 41 and an electromagnetic clutch 30 has the images recorded thereon as it passes the point A, at which it is exposed to a light beam modulated by the received image signal and arranged to scan the film in parallel paths at right-angles to the direction of the film, after which the film passes, successively, a first and second marking device 26 and 27, contact devices 14 and 19 and a cutting device 28. The marking device 26, which is operated electromagnetically, is arranged to mark the film (e.g. to punch a hole therein) when the signal which is transmitted between images ceases and thereby indicates the commencement of a picture transmission. The mark thus produced serves to operate a contact-device 14 when the film passes thereunder and thereby operates the second marking device 27 which is arranged to mark the film, on the edge opposite to that marked by device 26, so that the second mark does not operate contact device 14, but does operate contact device 19, the latter device preparing the operating circuit of the cutting device 28 which becomes operative to cut the film after an interval which is determined by the closing of contacts d in the circuit of the cutting device. These contacts are operated by means of a cam 38 which is driven from the main transmission system through an electrical coupling 37 and arranged so as to rotate through a definite angle (determined by a stop, not shown) and then to return, on being released, under the action of a spring 40. To ensure that the film is cut in definite lengths (e.g. about 50 cms.) and, when no image signals are received, that the marking devices and the film moving and cutting mechanisms are rendered inoperative, a further series of contacts b1, b2, b3, operated by a cam 35, and a contact e, operated by a cam 38, are arranged to control the above devices and mechanisms through a system of electromagnetic relays (Fig. 2, not shown).