Patent GB-748262-A (GB)
Title: Improvements in or relating to a method of transmitting electrically pictures, drawings, texts or the like
IPC: H04N1/12
Filed: 1951-05-28
Abstract: 748,262. Facsimile telegraphy. HELL, R. May 28, 1951 [May 2, 1949], No. 12510/51. Class 40 (3). In a facsimile transmission system in which a recording is made on a sheet or tape to represent the picture or text to be transmitted, the sheet or tape is secured by an element to derive electrical signals representing changes from black to white along a plurality of successive parallel bands of finite width extending across the picture or text, and the scanning element and/or the recording is, or are, such that the signals produced represent changes from black to white within the respective bands solely in the direction of scan and not transversely thereto. In the diagrammatic illustrations of Figs. 1, 2 the characters which are specially formed by a photographic or a printing process are modified in shape so that changes from black to white occur in the horizontal direction of the scanning bands, indicated by five parallel lines in Fig. 1, and by nine lines in Fig. 2, to provide for the transmission of capital and special letters. Figures or letters which have, inclined portions such as A, K, 7, &c. are preferably formed, indicated for the letter K in Fig. 2, with disconnected, staggered black portions which present no variation in the direction of the width of the scanning band. The message or text to be transmitted may be produced by means of a typewriter with type characters specially formed and the width of the scanning band may be less than the width, transverse to the direction of scanning, of the black portion (Fig. 7, not shown). At the receiver, the impulses corresponding to the black portions are arranged to print enlarged or widened areas so that a complete figure or letter is reproduced. The sheet 1 carrying the characters to be scanned is formed with edge perforations 2 which permit the sheet to be stepped after the complete scanning of a line of characters. In the transmitter, Fig. 8, the line of characters is scanned by apertures 14 in a moving band 15 associated with a longitudinal slit 13. A linear light source 16 is focused by a lens 17 on to the slit 13 and a longitudinal internal reflecting member 18 transmits the varying light response to a photo-electric cell 19. The sheet 1 is advanced at the end of each line by a shaft 10 with wheels 8, 9 provided with teeth engaging the perforations 2 in the sheet 1, an intermittent driving device 11<SP>1</SP> being operated by gear 11. In a modification, Fig. 10, impulses corresponding to the scanning of a letter in five parallel bands are recorded on a tape 20 by magnetic heads 22a ... 22e, the impulses being determined by bars 25 set by a key lever 26 and passed by rotating distributers 23 to the five heads 22. The first band of the successive characters are recorded on the tape 20 between the heads 22a and 22b, the second bank between 22b and 22c, and so on, so that the tape 20 will carry the impulses corresponding to the scanning of the five bands in succession. In a further modification, a transmitter employs a tape with perforations corresponding to the pulses representing the scanning of the matter in a number of parallel bands. In the recording apparatus, Fig. 13, the sheet 1 is fed slowly past a recording mechanism comprising a blade 44 operated by a magnet 48 in response to the received signals to press the sheet and an inking band 45 against a stud 42 carried on a band 41 traversed across the sheet. At the end of the reproduction of a complete line of characters, a stud 43 closes contacts 56 energizing a magnet 57 operating a pawl 58 and ratchet 55 to advance the sheet 1 by a distance corresponding to the spacing between successive lines of characters. In a modification, Fig. 15, 16 (not shown), a carriage carrying a printing stud is reciprocated across the electromagnetically-operated blade member and is driven in the forward and reverse directions by oppositely rotated threaded shafts engaging threaded members on the ends of an arm secured to the carriage. Line-spacing is effected by a pawl operated by a cross-shaped member with arms conjointly operated by two cams separately driven from the driving motor. In a further modification, Figs. 17, 18 (not shown), an inking roller is reciprocated across the record sheet by a threaded shaft which is reversed at the end of each line, and line spacing is effected by a ratchet and pawl mechanism operated by a specially-shaped cam. In a further modification, Figs. 21, 22, the spacing between the printed characters is effected by a discontinuous helical ridge 83 on a rotating drum 82 associated with a printing bar 84 mounted by pairs of leaf-springs 92 in a plate 86 held against a supporting surface 93 and rocked by a cam 85 rotated, in the arrangement described at one-eighth of the speed of rotation of the drum 82. The received signals are applied simultaneously to the magnets 48 so that the bar 84 is moved forward parallel to its inclined position, as determined by the cam 85, to press the inking ribbon 45 and sheet 1 against the appropriate portion of the multitum spiral ridge.