GB592797A - Improvements in or relating to communication systems and apparatus - Google Patents

Abstract

592,797. Type printing telegraphy; valve circuits ; thermionic distributers. NATIONAL CASH REGISTER CO. May 19, 1944, No. 9748. Convention date, Feb. 25, 1943. [Classes 40 (iii) and 40 (v)] In a telegraph system in which bursts of signals representing symbols are set from an electronic impulse generator at the sender to a receiver over a single channel, each burst comprising a number of substantially identical signals according to the symbol to be transmitted, a number of groups of electronic. devices are provided at the receiver, means being provided at the receiver which operates during the intervals between the bursts to route each to a different group, each group being controlled by the number of signals in the group to set up a direct representation of the associated symbol. The system described is similar to that described in Specification 592,796 bursts of impulses being transmitted with spaces between successive bursts and at the receiving end control impulses are generated during the spaces, to route the bursts to the correct bank of counting tubes. Fig. 1 shows a bank of gasfilled tubes which fire in succession after the tube connected to the depressed key has been fired by an impulse from a " start " tube, Fig. 6 (not shown). Condenser 163 delays the potential rise of the grid of the " shift " tube due to tube (0) firing thus delaying the firing of the '' shift " tube so that a space is provided between one burst of impulses and the next. The negative impulses are transmitted to terminal 335 on the control impulse generating means, Fig. 7, at the receiver. Tubes 340, 341 are connected as a trigger pair, tube 340 being normally conducting, as are tubes 337 and 343, while tube 342 is cut off. Negative impulses applied to the grid of tube 337 render it non- conducting so that its anode potential rises and positive impulses are applied through condenser 396 to the grid of tube 341 causing it to conduct, thus cutting off tube 340. The positive impulses from tube 337 applied through condenser 439 reduce the bias on the grid of tube 342 causing it to conduct. The drop in anode potential is applied to the grid of tube 340 to prevent it conducting. The values of condenser 425 and 'resistor 426 in the anode circuit are such that, when valve 342 becomes non-conducting after each impulse, its anode potential only rises slowly so that the next impulse arrives before the bias on tube 340 has been reduced sufficiently to cause it to conduct. Tube 340 thus remains non-conducting during the bursts of impulses but conducts again during the intervals between bursts. When tube 340 conducts a negative impulse is applied to the grid of pulse sharpening tube 343, cutting it off and producing a positive control impulse at terminal 462, which is applied to the routing means as in Specification 592,796. Positive impulses from the anode of valve 337 are fed selectively to the corresponding banks of counting tubes, selected by the routing means.