Patent GB-705502-A (GB)
Title: Improvements in and relating to the electrostatic storage of information
Inventor: WILLIAMS FREDERIC CALLAND
IPC: G11C11/23
Filed: 1950-07-20
Abstract: 705,502. Digital electrical calculating-apparatus. NATIONAL RESEARCH DEVELOPMENT CORPORATION. July 11, 1951 [July 20, 1950], No. 18204/50. Class 106 (1). [Also in Group XL(c)] In a method of storing digital information by the bombardment with an electron beam of an insulating screen in a cathode ray tube and its subsequent exploration as described in Specifications 657,591, 705,474 and 705,498, the beam is held stationary during each digit interval and two H.F. oscillations are applied one to switch on and off the beam during a part of each cycle of oscillation and the other to vary the potential difference between the screen and the collecting electrode of the C.R. tube. The two oscillations have at least two different conditions in which the potential difference between screen and collecting electrode when the beam is switched on differ : one digit is recorded by using one such condition during the digital interval and another digit by following this by a period during which a second condition prevails. Fig. 1 shows a C.R. tube store in which digital information is writtenon to or taken-off from the pick up plate 11 associated with the screen of the C.R. tube 10. H.F. oscillations from oscillator 19 as shown in Fig. 2 (d) are applied via filter 21 to the pickup plate 11 and are also applied via gates 23, 25 to the grid 12 of the C.R. tube via modulator 22 the path to gate 25 also including a phase inverter 24. Gate 25 is open for the dot period t1, Fig. 2 (a), of each digit interval and gate 23 for the dash-dot period 27, Fig. 2 (c), and modulator 22 passes R.F. oscillations only for the duration of positive pulses applied to it from gate 23 or 25. The C.R. beam is deflected to scan a raster on the screen and a stepped waveform is applied from the X scan generator so that the beam is stationary for the digit interval t2, Fig. 2 (b). With no information fed in at terminal 28 the output from unit 14, which may be of the type described in Specification 682,156, to modulator 22 consists only of dots which occur whilst gate 25 is open and gate 23 closed. The C.R. beam is thus turned by the peaks of the R.F. oscillations applied via gate 25, i.e. oscillations, Fig. 2 (e), which are in anti-phase to those on the pick-up plate 11 and dots are recorded over the whole C.R. screen. When a dash is applied from unit 14 to modulator 22 the gate 25 is open for time t1 to pass pulses of anti-phase R.F. oscillations as in Fig. 2 (e), followed by the opening of gate 23 for time t2- t1 to pass pulses of in-phase R.F. oscillations as in Fig. 2 (f). The charge left on a given area of the screen in this latter case differs from that when dots only are applied and on subsequent scanning a dash will be generated at the output of unit 14. In a modification the digit interval is divided into two dot periods one or both of which are used to convey the two different kinds of information respectively. A negative "read" signal may be employed and the effect of negative cloud effect may then be eliminated as described in Specification 705,493. In order to store information of more than two kinds the required different states of charge may be obtained by amplitude modulation of the R.F. oscillations applied to the signal plate or by the use of phase relationships in addition to in-phase and antiphase between the two R F. oscillations applied to the grid and pick-up plate respectively of the C.R. tube.