Patent GB-711779-A (GB)
Title: Improvements in or relating to electronic information storage systems and discharge tubes therefor
Inventor: WATERS PAUL LORAINE
IPC: G11C11/23
Filed: 1950-07-07
Abstract: 711,779. Electric digital data storage apparatus. NATIONAL RESEARCH DEVELOPMENT CORPORATION. July 2, 1951 [July 7, 1950], No. 17100/50. Class 106 (1). [Also in Group XL(a)] A cathode-ray information storage system comprises a storage target formed as a mosaic of insulating elements on a conductive plate and one or more guns which can be operated (a) above the first secondary emission crossover point to bring target elements to a positive potential, for ,erasing (b) above the crossover point for positively charged elements and below the crossover point for negatively charged elements, for maintaining a desired charge pattern during reading and at other times, and (c) below the crossover point for positively charged elements to send them negative, for writing. The target may be made by (a) anodizing an aluminium plate and engraving the insulating surface to divide it into discrete areas, (b) depositing luminescent material on a metal plate through a fine mesh screen to give about 50 per cent coverage, (c) spraying insulation by an atomizer on to a metal plate. The element size may be greater or less than the beam cross section. In the preferred embodiment, Fig. 3, there are two guns with cathodes 4, 7, accelerating and focusing electrodes 5, 8, and decelerating electrodes 6, 10. The gun 4, 5, 6 produces a scanning or flooding beam of such energy (greater than 50 volts) that the secondary emission ratio of the target is greater than unity and the insulating elements are driven positive to about the potential of collector 3 (+ 10 volts say) the metal target plate being earthed. The bombarding energy is then reduced to 60 volts, say, leaving the secondary emission ratio still greater than unity. The gun 7, 8, 9 is now polarized at the mean writing potential, i.e. 30 volts negative to earth which gives an electron velocity of 40 volts, i.e. so the secondary emission ratio is less than unity for the particular elements scanned (by deflecting plates 9). These elements are consequently driven negative to - 30 volts, and gun 4, 5, 6 being left on drives them to - 60 volts where they are stabilized. For reading the information, gun 7, 8, 9 is polarized to - 60 volts, i.e. the .same as gun 4, 5, 6 which is still left on, and it is shown that an output signal representing the information can be taken off the metal plate via resistancecondenser combination 17, 18 without destroying the information recorded on the target. For erasing, gun 7, 8, 9 is polarized to - 120 volts so the secondary emission ratio is greater than unity for all parts of the target and the negative areas are consequently driven positive again. Output signals in reverse sense can be derived from the target plate during erasure. The different potentials of gun 7, 8, 9 are controlled by switch 11 which may or may not be an electronic one. To avoid a false interpretation of these signals on erasure, operation of switch 11 may introduce an additional inverting stage into the output amplifier. Modulator switch 15 allows signals to be written in to the storage target. The signals may be binary digits or may represent a " black and white " picture or diagram. Intermediate tone values may be achieved by control of the sizes of the insulating elements analogous to that used in the half tone printing process. Collector 3 may or may not be a wall coating. To write in a line of binary digits, for example, in an electronic digital computer, beam from gun 7, 8, 9 is scanned along a line and the beam turned on at the appropriate instants by modulator 15, and by scanning a raster in this way the desired number of lines may be built up. It is stated that by discontinuous scanning, or modulation in continuous scanning, signals may be read and/or erased from any desired part of the target. Partial writing can also be achieved. The holding, reading, writing and erasing functions may be performed by separate beams, or alternatively by using interlaced scanning a single beam can combine these three functions with the holding function.