Patent GB-800561-A (GB)
Title: Improvements in or relating to barrier grid storage tube circuits
IPC: G11C11/23
Filed: 1956-07-31
Abstract: 800,561. Electric data digital storage apparatus. WESTERN ELECTRIC CO., Inc. July 31, 1956 [Aug. 2, 1955], No. 23594/56. Class 106 (1). [Also in Group XL (a)] A circuit comprising a barrier grid storage tube has means for regenerating the binary information stored, immediately after reading, and/or for altering the state of any element from 0 to 1 or vice versa; an output pulse is withdrawn from an elemental area of the target of the tube only when the charge on the area exceeds a predetermined value (binary one) and is used to generate a second pulse which is fed to the tube input to regenerate the charge on the area. The regenerating means comprises an output amplifier 42 having an odd or even number of stages to give a positive output pulse to coincidence gate 43 to which is also fed 45 degrees reading pulses from generator 35, pulse delay generator 44 which is operative only if the target element is charged to a binary " 1," second coincidence gate 46 to which is fed the output from 44, and 120 degrees writing pulses from pulse generator 36. The output from 46 is fed via driving amplifier 47, which has an even or odd number of amplifying stages to give correct writing polarity to the input (back plate) terminal 17 of the storage tube. Coincidence gate 43 only gives an output when there is a binary " 1 " pulse from 42 overlapping a reading pulse from 35 and coincidence gate 46 when the pulse from 44 overlaps a writing pulse from 36, the waveforms and phasing being discussed with reference to Fig. 2a (not shown). For a binary " 0 " there is no output from 42, 43, 44, 46 or 47 and hence no change in the potential of the target element. The regenerating operations are controlled by a " logic " circuit 48, 49 which can also by supplying negative pulses of its own, cancel the output of 44 (thereby converting " 1 " to " 0 ") or give a positive pulse input to 46 when 44 has no output (thereby converting " 0 " into " 1 "). After regeneration or substitution as above the beam is blanked and the beam moves on to the next storage area, and the regenerating scans keep repeating. The coincidence gates 43, 46 may be multi-grid vacuum tubes with the two inputs applied to separate grids. The reading and writing parts are conventional; writing may be positive or negative, reading being correspondingly negative or positive. The reading pulse is made up of secondaries collected by output electrode 18 surrounded by shield 19. Positive writing is faster than negative writing, but negative writing is erased more quickly. The target comprises a mica sheet having an earthed barrier grid on one side and a conducting back plate on the other, input (writing signals) being applied to the back plate. The frequency of generator 25 (245760 cps.) is counted down by 6 stage binary counter 26 to 3840 cps. (the horizontal scanning frequency) which energizes staircase generator 38 producing the horizontal scanning, and is further counted down by a similar 6 stage binary counter 27 to 60 cps. (vertical scan frequency) part of which is compared with a standard 60 cps. in a phase comparator 28, the output of which is fed via reactance tube 29 to stabilize the frequency of source 25, while another part energizes sawtooth generator 40 to energize the vertical deflection plates and to generate frame blanking pulses in differentiator 41 which are supplied to control grid 12 via adder 37. The line blanking pulses are supplied by counter 26 through staircase generator 38, differentiator 39 and adder 37. Generator 25 also supplies a phase splitter 30 which energizes through circuits 31, 32, 33, each comprising a phase shifter, amplifier and wave squarer, pulse generators 34, 35, 36 providing 120 degrees spot blanking pulses to control grid 12 via adder 37, 45 degrees reading pulses to gate 46 and 120 degrees writing pulses to gate 46. The regenerating part of the circuit is described in detail with reference to Fig. 3 (not shown). Amplifier 42 comprises four pentodes, the coincidence gates 43, 46 each a single pentode, pulse delay generator 44 is a double triode multivibrator and driving amplifier 47 two pentodes. The device is used in telephone or computer circuits. The stored signal can be read several times or looked at periodically and held for a long time.