GB475239A - Improvements in multiplex telephony and the like - Google Patents

Abstract

475,239. Multiplex transmission. HENROTEAU, F. C. P. March 1, 1937, No. 6080. Convention date, Jan. 16. [Class 40 (iv)] [Also in Group XL] In a system of the kind in which elementary portions of several messages are recorded and are then reproduced in succession at a high speed for transmission, recording and reproduction at both ends of the system are effected by " kinescopes " in which a soundmodulated or signal-modulated cathode ray makes a temporary trace on a fluorescent screen and " iconoscopes " which comprise a screen formed from innumerable photo-electrically charged condensers which are scanned by a cathode ray. The sound traces made by kinescopes corresponding to several channels are optically projected onto the screen of an iconoscope which is completely scanned in the time taken by the rays of the kinescopes to make a single traverse. The variable currents produced by the discharge of the elementary condensers, or by secondary emission may be used for transmission. In the latter case use is preferably made of electron multipliers. The resulting currents at the receiving end produce a number of fluorescent record traces on the screen of a kinescope which is scanned in two directions and these traces are transferred to iconoscopes individual to the respective channels. To avoid waste of time while the scanning ray is moving from one record trace to the next, several kinescopeiconoscope groups may be arranged to work together as shown in Figs. 2 and 4. The voltage controlling the vertical deflection acts in the same way on all the iconscopes but that controlling the horizontal deflection becomes effective on each of them in turn owing to the effect of initial bias voltages provided by a potential divider. Transmission may be effected by carrier waves of a length of a few centimetres.