Patent GB-607711-A (GB)
Title: Electric signal transmission system
IPC: H04L21/00
Filed: 1945-10-29
Abstract: 607,711. Facsimile telegraphy; transmitters; thermionic distributers. STANDARD TELEPHONES & CABLES, Ltd. Oct. 29, 1945, No. 28645. Convention date, June 18, 1943. [Class 40 (iii)] An electric signalling system for the production of visible characters by impulses dependent upon the shape of the character, when subdivided into a number of bands, comprises a master electronic counter circuit with a number of sequentially operated gas-discharge tubes and divided into a number of electronic subcounter circuits corresponding to the number of bands, each gaseous discharge tube providing a pulse, and the number of tubes in each subcounter circuit being equal to the maximum number of impulses constituting a band and means for starting and stopping the master counter circuit and controllable switch means for determining the transmission of pulses in accordance with the shape of the desired character. The impulses to be transmitted are determined by switch members 40a ... 40g, 42a ... 42g, 44a ....44g .... , carried by key levers 38 corresponding to the characters. The output conductors from the sub-counter circuits 12a ... 12g are connected through banks of resistors 1a... 7a, 1b .. 7b, ... 1g. .. 7g and selectively by the switch members 40a ... , 42a ..., 44a ... , to the suppressor grid of a gating 'valve 22 which controls the passage of current from a high-frequency oscillator to modulate a carrier. In the transmission, for example, of the letter E, the switch 40a is connected to each of the banks 1a ... 7a so that seven successive impulses are passed over leads 350 and 268 to the gating valve 22 corresponding to the first band. A single impulse is passed during the first period of the second and third bands over banks 1b, 1c by switches 40b, 40c and for the fourth band the switch 40d is connected to the counter circuit 12d so that impulses pass to the tube 22 during the first, second, third and fourth periods pertaining to that band. The fifth and sixth bands comprise single pulses derived from circuits 12e, 12f under control of switch members 40e, 40f and the seven impulses for seventh band are derived from circuit 12g and the switch member 40g. On the depression of a key 38, switch 30 connects ground to the grid of the first tube 14a of the first subsidiary counter circuit 11a which fires, passes an impulse to its output leads 1a and biasses the grid of the second valve 14a which fires and extinguishes the previous valve. The sub-counter circuits are operated in succession with a delay provided by coupling condensers between the last tube of one circuit and the first tube of the next circuit, and the final circuit includes an additional valve 14<1>g, which on operation brings the first valve 14a into operation to recommence the cycle. Each completion of the cycle with the consequent operation of valve 14<1>g applies a charge to a condenser 209 which, after a predetermined number of operations, is charged to a value such that when the valve 14<1>g is extinguished the first valve 14a of the first sub-counter circuit cannot be operated. The receiver, Fig. 5 (not shown), comprises a cathode-ray tube operating in a manner generally similar to that described in Specification 587,405, but modulated by the received impulses in its scanning from left to right instead of during the up-and-down motion.