Patent GB-787085-A (GB)
Title: An electronic delay circuit for use as a digital data store
Filed: 1955-04-22
Abstract: 787,085. Electric digital-data-storage apparatus. INTERNATIONAL BUSINESS MACHINES CORPORATION. April 22, 1955 [April 27, 1954], No. 11673/55. Class 106 (1). [Also in Group XXXV] A cyclically operated device for storing an electrical impulse representing data by its timing within a cycle of operation of the device includes a capacitor, means adapted to charge said capacitor upon receipt of the impulse to be stored, circuit means connected across said capacitor for permitting said capacitor to discharge, means including a multi-grid tube having one control grid connected to receive the potential across said capacitor and another control grid connected to receive cyclically recurring trains of character representing impulses, and means co-operating with all the afore-recited means for recharging said capacitor and generating an electrical output impulse at a point in each cycle representative of the data to be stored. When the device receives a decimal digit represented by a single pulse differentially positioned in a ten-point cycle, Fig. 2, it produces a similarly positioned output pulse in each following cycle. In principal a pulse to be stored causes the charging of a condenser 18 which then discharges in a circuit so arranged that after ten cycle points it is recharged again. To enter a seven, for example, an input triode 32 is caused to conduct at the beginning of cycle point seven. (As shown, this is achieved by removing a cut-off bias from control grid 32g-see also Fig. 2.) When it ceases to conduct a positive pulse 27k Fig. 2, is transmitted via a condenser 31 to a cathode follower 34 which causes a triode 20 to conduct and lower the potential of the lower plate of condenser 18 (see 11cg1, Fig. 2). Towards the end of cycle point 7, triode 20 is positively cut-off by a "space impulse which being applied to the grid of a triode 29 causes the potential of the cathode 27k of triode 27 to fall to its usual negative value. Condenser 18 now starts discharging through resistors 16, 17 and 12, and the potential of the first control grid of tube 11 begins to rise. Throughout the operation of the device " number impulses," Fig. 2, are being applied to the second control grid of tube 11, and these cause, because of inter-electrode capacitances, pulses to be induced on the screen grid of tube 11 (11scg, Fig. 2), which pass via a condenser 23 to the grid 27g, Fig. 2, of a triode 27. They have no effect on the triode however because of the large negative cut-off bias applied to the grid from a potentiometer 24, 25. As condenser 18 continues to discharge, first, after eight cycle points screen grid current begins to flow, and second, after ten cycle points, with a number pulse on the second control grid, the tube fires. It immediately cuts itself off however by the negative pulse transmitted via condenser 18 from the anode to the first control grid, but more important, the large positive pulse transmitted by the screen grid causes triode 27 to conduct which, in turn, causes triode 20 to conduct, and as triode 20 will not be cut-off until the beginning of the next space impulse the discharging of condenser 18 is inhibited until then, and thus the start of each discharge period is accurately synchronized. The whole process is then repeated indefinitely until a new number is entered. Output pulses are available from a cathode follower 58 each time triode 20 fires. In order to maintain the " discharge " time of condenser 18 constant, the voltage of the cathode of tube 11, line 14, is maintained at half the voltage of the high-tension line 13, by a voltage stabilizer 15 (see Group XXXV).