GB712643A - Improvements in or relating to electrical gas discharge tube circuits - Google Patents

Abstract

712,643. Digital electric calculating apparatus. STANDARD TELEPHONES & CABLES, Ltd. Dec. 20, 1951, No. 29858/51. Class 106 (1). [Also in Group XL(c)] Fig. 2 shows a storage element in which the condition to be stored is represented by a positive pulse applied at I which is of sufficient amplitude to fire the trigger electrode-cathode gap only of the gas-filled cold cathode tube V2. To verify whether the stage is in the stored condition a positive pulse is applied at P to the anode of the tube via rectifier MR1, if the tube is in the stored condition the main anode/ cathode gap fires and a positive pulse is produced at the cathode. The cathode potential is prevented from becoming more negative than -50 volts by the "catcher" rectifier MR2, so that until the cathode voltage rises above 50 volts the impedance of the cathode load is equal to the forward resistance of rectifier MR2. When the tube is in the stored condition and is tested the anode pulse applied at P is gated through the stage, rectifier MR2 is blocked and the cathode impedance is equal to that of resistor R2. Thus the stage has effectively a variable cathode load so that it is possible to obtain a large amplitude output pulse whilst still keeping within the operating limits of the tube. In a modification shown in Fig. 3 four storage tubes VI-V4 have their cathodes connected via rectifiers to a common load R4 and a "catcher" rectifier MR2: Each tube has a separate input to its trigger electrode and the "storage" state of a tube is tested by applying a positive pulse to its anode via rectifiers at inputs P1-P4. The circuit may be used for storage in a binary code of a single decimal digit a discharging tube representing the binary digit 1 and a non-discharging tube the digit 0 so that on testing the tubes in sequence a pulse train is developed at the output 0 which represents the binary coded value of the digit. Fig. 6 shows a stage of a binary counter in which tubes B1, B2 are connected by capacitor C2 to function as a binary pair the output " carry pulses from which are gated through an interstage coupling tube B3, when it is rendered conductive. In a modification (Fig. 7, not shown) the " carry" " pulse is taken from the cathode circuit of one tube of the binary pair. Fig. 8 shows part of a counting chain comprising two tubes having a common anode load R8 in which when an incoming pulse applied to a trigger electrode fires a tube the previously fired tube is extinguished by the voltage drop in resistor R8. The driving pulse is gated to the cathode of the previous tube via rectifier MR5 as well as to the trigger electrode of the tube to be fired.