Patent GB-680340-A (GB)
Title: Improvements relating to electronic counting apparatus
Inventor: RODDA SIDNEY
IPC: H03K29/00
Filed: 1949-07-08
Abstract: 680,340. Electronic counting apparatus. EDISON -SWAN ELECTRIC CO., Ltd. July 6, 1950 [July 8, 1949], No. 18148/49. Class 106 (i). [Also in Groups XXXV and XL (c)] Counting-apparatus having a plurality of stable states comprises a cathode-ray tube having a screen formed and arranged to present a plurality of localized areas of fluorescent material arranged along one of the deflection axes of the electron beam, means for deflecting the beam to impinge upon any one of such areas and to remain stable thereon and means forcausing the beam to be deflected from one such area to the next adjacent area upon the arrival of a signal pulse to be registered. The apparatus may be adapted for counting with a radix of any value but is shown for counting in the binary notation. The end of the cathoderay tube T adjacent the fluorescent coating 3 is covered by an opaque screen 2 having three slots 4, a, 6. When the tube is registering-zero, the electron beam is deflected by the plates Y, Y<SP>1</SP> so as to fall on the upper slot 4. An alternating potential is applied to the X deflecting plates to cause the beam to sweep in a horizontal line. The beam is held on the slot by a control circuit including a photo-multiplier cell 7. Light from the slot falls on the cathode of the cell 7 and the consequent flow of current in the cell causes a drop in the potential of its anode which is connected to the deflecting plate Y<SP>1</SP>. This deflects the beam downwardly but as it is lowered, light is cut off by the slot and the current in the cell 7 decreases, thus restoring the potential of the deflecting plate Y<SP>1</SP> and so raising the beam once more. Electrical (negative) pulses, which may be generated by an unstable trigger pair of hard valves, to be counted are applied to the deflecting plate Y<SP>1</SP> and are of such an amplitude that each switches the beam from one slot to the next lower slot where it is held by the photo-cell control circuit. The pulses to be counted may alternatively be in the form of light pulses applied to the cell 7. In order that the proper potential may be applied to the deflecting plate Y' to hold the beam on any slot, the slots may increase in width (horizontally) downwardly. Thus, the lower the slot, the greater the amount of light falling on the photo-cell and the lower the potential of the deflecting plate Y<SP>1</SP>. The same effect may be achieved by using optical filters in front of the slots. The nth pulse, where n is the radix of the counting system used, switches the beam to the lowermost slot 6, light from which falls on an additional photo-multipliercell 8 and is screened from the cell 7 by a screen 9. The anode of the additional cell 8 is connected to one of the secondary cathodes of the cell 7 so that when the beam is deflected on to the lowest slot, the cell 7 is rendered non- conducting and the potential of the deflecting plate Y<SP>1</SP> is raised to restore the beam to the highest slot. Alternatively, the pulse at the anode of the additional cell 8 may be used to deflect the beam horizontally from the slot or be applied to the grid of the electron gun of the tube so as to cut-off the beam in order that it can return upwardly. This pulse is also used to produce a transfer pulse for application to the tube of next higher order. The components of the cathode-ray tubes of several orders may be housed in a single envelope. The slots may be duplicated in order to indicate the digit registered or a current-measuring instrument may be arranged in the photo-cell circuit for this purpose.