Patent GB-632165-A (GB)
Title: Improvements in or relating to distributors for sequentially controlling different circuits
IPC: H04L13/14
Filed: 1946-08-29
Abstract: 632,165. Thermionic distributers; typeprinting telegraphy. INTERNATIONAL BUSINESS MACHINES CORPORATION. Aug. 29, 1946, No. 25946. Convention date, Oct. 18, 1945. [Class 40.(iii)] [Also in Group XL (c)] A telegraphic-receiver or like distributer is characterized by the fact that the signal elements are transmitted to code storage devices through corresponding gaseous trigger tubes, each having two control grids, the tubes having the potential on one grid raised in succession to a point where the tube will conduct unless blocked by the signal potential which is applied concurrently to the other grid of all the tubes. The receiver shown is arranged for a six-unit start-stop code. Signals consisting of tone for spaces and no tone for marks are applied via a jack 15, volume control 16, amplifiers V<10> and V<11>, and a rectifier V<12> to a resistance 27. An incoming start signal (space) produces a potential as shown across the resistor 27, applying a negative potential to the grid of a normally conducting valve V<13>, which is extinguished. The collapse of the anode current in the primary of transformer T<12> induces an e.m.f. in the secondary and an associated delay circuit 37, 38, 39 so that after a delay of half a signal-element the gas-discharge tube G<9> fires through a valve V<9>, normally conditioned to conduct. The consequent potential drop across cathode resistor 40 extinguishes the normally conducting valve V<8>. The flux in the primary of transformer T collapses and an e.m.f. is built up in the secondary and applies a positive potential over connection X to the grid of a sequence tube V<1>, which conducts. The consequent grid current delays the collapse of the secondary e.m.f. until, after a signal-element duration, the grid reaches cathode potential and the valve ceases to conduct. The consequent impulse in the secondary of anode transformer T<1> swings the grid of V<2> positive and V<2> similarly conducts for a signal-element period. Each sequence valve V<1> ... V<6> thus conducts in turn and sends a positive impulse when it ceases to conduct to the control grid of an associated gas-discharge tetrode G<1> ... G<6>, the screen grids of which are connected over lead 61 to the input resistor 27. If at the time a particular control grid receives a positive pulse from its associated valve V<1> ... V<6>, a mark is being received, the bias supplied by the input resistor 27 to the screen grid allows that tetrode to fire, the arc being sustained over an anode resistor 56. Thus at the end of a received signal those of the code tubes G<1> ... G- corresponding to marks will remain conducting. When valve V<5> conducts it fires tube G<7> over lead 64 to energize a print relay R<1>. Due to the time required to energize this relay it operates just after V<6> is extinguished and its contacts R<1>a ... R<1>f energize those code magnets M<1> ... M<6> whose corresponding tubes G<1> ... G<6> have fired, thus printing a character or performing a function in any well-known manner. When the sequence valve V<6> ceases to conduct, V<7> conducts and over a connection Z, Z sends a negative impulse to the grid of valve V<9>, breaking the circuit of the start tube G<9> for a period of one signal-element, determined by condenser 68. When, after a period of two signal-elements, V<7> ceases to conduct, it fires G<8>, which extinguishes G', releasing the print magnet R<1> and hence the code-magnets M<1> ... M<6>. As G' is extingushed an oscillation is set up in the oscillatory circuit comprising the winding R<1>, condenser 72 and resistor 70, the first negative half-cycle of which extinguishes the tube G'. The tubes G<1> ... G<6> are similarly extinguished by an oscillation set up in the circuit resistor 56, resistor 74, condenser 73 and winding of the appropriate magnet M<1> ... M<6>. The circuit is now restored to normal. The anode, cathode and bias potentials are all obtained from tappings on a potential divider 4 ... 10 supplied by A.C. mains via a plug 1 and full-wave rectifier 2. A rise in anode voltage, due to mains variation, is accompanied by a rise in cathode and bias voltage and the tappings and characteristics of the sequence valves V<1> ... V<6> are so arranged that variations in mains voltage of the order of plus or minus 10 per cent have virtually no effect on the timing of the sequence tubes. A potentiometer 9 allows the bias of the sequence tubes to be adjusted so that their period of operation corresponds to that of the received signal-elements. Specification 532,633 is referred to.