Patent GB-690050-A (GB)
Title: Improvements in or relating to electronic calculating machines
IPC: G11C11/28
Filed: 1950-06-20
Abstract: 690,050. Digital electric calculating-apparatus. SOC. CIVILE D'ETUDES DE CALCUL AUTOMATIQUE (S.C.E.C.A.). June 20, 1950 [June 21, 1949], No. 15444/50. Class 106 (i). A memory device for an electronic calculating machine comprises a group of gas-filled electron tubes, across each of which is normally applied a voltage which is between the striking and extinction voltages, and means for selectively applying pulses to the tubes. Memory devices. Each memory device, e.g. 10 or 10<SP>1</SP>, for storing digits of a binary notation, comprises a glow tube 1a for each order. One electrode of each tube is connected through a resistance to a +65 v. supply and the other electrode is connected through resistances 20a and 34 and a line 14 to earth and through a resistance and capacity in series 21a and a line 12a to the anode of a pentode 23 associated with the corresponding order 11a of a binary electronic calculating device. The control grid of this pentode is connected to one anode of a double-triode trigger pair so that its potential is just below cut-off or well below according to whether the trigger pair registers 1 or 0. On receipt of a positive entry-control pulse at a point C, capacity-coupled to the control grid, a temporary drop in the potential of this anode produces a pulse of - 120 v. at the connected electrode of the glow tube which is of sufficient duration to fire the glow tube, if one is registered in the order 11a. The glow tube remains conducting since the voltage normally applied across it is greater than the extinction voltage. Each memory device is associated with a selecting circuit, e.g. 13 for the memory device 10, by which an entry may be prevented. A positive pulse is applied to a point E at the same time as the entry-control pulse and is applied to the control-grid of a pentode 33 arranged in a cathode-follower circuit, to produce a pulse of + 120 v. on its cathode which is connected, via the line 14, to negative electrodes of the glow tubes of the corresponding memory device. The pulse is of such short duration as to be ineffective to extinguish conducting glow tubes but effective to cancel part of the entry-pulse on the line 12a so that the remaining part of that pulse is ineffective. A memory device may be zeroized by applying a longer positive pulse to the control grid of the pentode 33 associated with the device. Reading out. Associated with each order of the memory devices is a reading-out circuit and associated with each memory device is a reading-out control tube (not shown), similar to the pentodes 23 and having its anode connected to the appropriate line 14 or 14<SP>1</SP>. When it is desired to read a memory device, a short negative pulse is produced at the anode of the corresponding control tube and is applied. via the line 14 or 14<SP>1</SP> to the negative electrodes of the glow tubes. If a glow tube is not conducting, the pulse is blocked by that tube but if a glow tube, e.g. 1a is conducting, its resistance is low and the pulse passes through a resistance and capacity in series 22a and a line 16a to the reading-out circuit 17a. A tube 37 amplifies and inverts the pulse which is then applied to the control electrode of a gas-filled triode 39, which fires to produce a pulse at a point S capacity-coupled to its anode. A switch 47 may be closed to render the tube 39 and the reading-out circuit ineffective during entry or cancelling operations.