Patent GB-786771-A (GB)
Title: Improvements in and relating to electrostatic information storage
Inventor: WILLIAMS FREDERIC CALLAND
IPC: G11C11/23
Filed: 1953-12-11
Abstract: 786,771. Electrical digital data storage apparatus. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Dec. 9, 1954 [Dec. 11, 1953], No. 34646/53. Class 106 (1). [Also in Group XL (a)] Storage and reading of digital information is obtained in a cathode-ray tube by bombarding an elemental area of the target whilst applying to an electrode in or near the target surface a first potential giving it a charge representative of one digit, and, when required to store a different digit on the area, bombarding it a second time whilst applying to the said electrodes a second potential giving it a different charge, the information being read during bombardment of the area with the electrode at the first potential, thereby generating a signal representing the digit stored on the area. A cathode-ray tube 10 has a target comprising an insulator 11, e.g. mica or a phosphor, a mesh 12 on the surface and preferably in contact therewith, and a signal plate 13. The mesh may be a single set of parallel conducting strips or two sets perpendicular to each other, their spacing such that the beam spot covers at least three parallel strips. A loop circuit comprising an amplifier and a pulse generator 15 couples the signal plate and the control grid of the tube. Oscillation generator 14 supplies H.F. oscillations of 5.0 and 5.1 Mc/s. to the signal plate 13 and the control grid respectively. The pulse generator 15 producing dot and dash extension pulses 17, 18 (Fig. 2) is locked to the 100 kc/s. beat and feeds to the control grid biasing it to a potential which switches on the beam during the positive peaks of the 5.1 Mc/s. oscillation. A stepped waveform potential applied to the X deflecting plates holds the beam on the elemental areas of the target for a digit interval. The signals generated at the pick-up electrode by the pulses applied to the control grid depend on the previous state of charge on the elemental areas and are shown in Fig. 2 (d), only a small negative pulse 26 being obtained when on the previous scan there had been no " dash " pulse 18. The generator 15 also produces strobe pulses which select from the waveform, Fig. 2 (d), and feed back to circuit 15 for regenerative purposes. Thus, strobe 27 selects the positive pulse 24 and releases a dash extension pulse 18 from generator 15 to regenerate the original charge on the surface. Information is written in by interrupting the loop circuit and applying suitable pulses to the generator 15. The RF oscillation is preferably applied to the mesh during the whole of the quarter cycle preceding the peak so as to approach the full value of charge storage. The tube may be biased permanently to be switched on by the highfrequency potentials on the control grid, and the oscillations applied in bursts to the grid on the occurrence of dot or dash pulses, but continuously to the mesh. In another preferred method, a sinusoidal oscillation of 100 kc/s. is applied to the mesh and in recording one digit the beam is switched on or intensified only in the first part of the interval, the mesh being driven negative (or positive) and in the second part for recording a second digit, or for regeneration, the mesh is driven positive (or negative) correspondingly. The 100 kc/s. component of the output is suppressed by a filter or by a bridge circuit, ceramic capacitors being avoided. In another form, two oscillations of the same frequency are used, that to the cathode being fed through two gating pentodes in parallel, giving the same or opposite phase to the oscillations as required.