Patent GB-677872-A (GB)
Title: Improvements in or relating to gaseous discharge tube counting chains
Inventor: RIDLER DESMOND SYDNEY
IPC: H03K23/82
Filed: 1950-11-02
Abstract: 677,872. Electronic calculating-apparatus. STANDARD TELEPHONES & CABLES, Ltd. Nov. 2, 1950, No. 26746/50. Class 106 (i). [Also in Group XL (c)] A counting chain of gas-filled discharge tubes comprises a coincidence gate circuit between each pair of consecutive tubes, each gate interconnecting the cathode of the first tube of a pair, the trigger electrode of the second tube and the common lead to which the triggering pulses are applied so that the second tube of a pair has a pulse applied to it and fires when the discharge of the first tube and a triggering pulse on the common lead occur simultaneously. Fig. 2 shows a section of a counting chain comprising gas-filled tubes T<SP>1</SP>-T<SP>3</SP> in which triggering pulses are applied simultaneously to all the stages from terminal P+. If tube T<SP>1</SP> is initially discharging so that its cathode is positive, rectifier W<SP>1</SP> is blocked and W<SP>2</SP> is conductive and a small positive potential appears at point X which even with the positive bias on the trigger electrode is insufficient to fire tube T<SP>2</SP>. On occurrence of the next positive trigger pulse at P+ rectifier W<SP>2</SP> is blocked, the potential at X rises and tube T<SP>2</SP> fires, tube T<SP>1</SP> being extinguished by the voltage drop produced across the common anode load resistor R<SP>1</SP>. In a modification, Fig. 3 (not shown), the trigger pulses are applied to each stage via a common gate circuit comprising two rectifiers and the point X of the inter-connection between each stage is brought out separately via a rectifier so that the chain may be stopped in any required position. In a further modification, Fig. 4 (not shown), a capacitor-resistor time constant circuit is included in the cathode circuit and between the anode and common anode supply lead of each stage, thus enabling the tubes to be operated with a high anode voltage which enables the deionization time to be shortened and the speed of operation of the counter to be increased whilst maintaining a low cathode output impedance. Fig. 5 shows a modification in which the cathode load resistors R<SP>6</SP> are returned to a negative potential and an additional rectifier W<SP>7</SP> is connected across each cathode capacitor C' which prevents the cathode voltage from falling below earth potential. When tube T<SP>1</SP> conducts current flow passes through rectifier W<SP>7</SP> and resistor R<SP>6</SP> so that capacitor C<SP>4</SP> is rapidly charged and when tube T<SP>1</SP> is extinguished capacitor C' discharges to the negative potential to which resistor R<SP>6</SP> is returned. Fig. 7 shows a coupling circuit in which an additional rectifier W<SP>8</SP> and an integrating circuit C<SP>6</SP>, R<SP>8</SP> produces a saw-tooth type cathode output pulse, the slowly rising pulse reducing the likelihood of two tubes firing simultaneously at high repetition frequencies. In a further modification, Fig. 8 (not shown), three tubes are coupled by circuits as shown in Fig. 7 to operate as a divide by three circuit, the cathode of each valve being returned to a high negative potential.