Patent GB-741687-A (GB)
Title: Improvements in statistical record card analysers
IPC: H04N1/00
Filed: 1953-06-08
Abstract: 741,687. Sensing record cards. INTERNATIONAL BUSINESS MACHINES CORPORATION. June 8,1953 [June 11, 1952], No. 15722/53. Class 40 (3). [Also in Group XIX] Record cards 9, Fig. 1, are moved continuously in the direction of the arrow so that each card presents a leading edge 11 to an illuminated slit 6. The slit 6 is illuminated by a light source 8 enclosed in a light-tight housing 15. The direction of travel by the cards and the arrangement of the slit 6 is such that illumination from the slit falls on each card column successively, the cards being punched, or provided with transparent areas, representing data in columns in the usual manner. Light passing through the perforations in a card column falls on the screen 17 of an iconoscope 16 to form an image of the column appearing in front of the aperture. The effective area of the screen 17 is composed of a narrow band of light-sensitive material 18 on an insulating film 19 backed by a conductive plate or output electrode 21. The iconoscope is provided with an electron gun 22 for projecting a focused beam of electrons to the screen 17 a grid 23, vertical and horizontal deflecting plates 24, 25, in the usual manner. A scanning and blanking circuit 26 holds the electron beam at a point A, when the leading edge of a card 9 crosses the aperture 6. A signal is produced at the output electrode 21 of the iconoscope across a resistor 27 and is passed to an amplifier 28 where it is amplified and fed to trigger the scanning and blanking circuit 26 into operation. The scanning and blanking circuit produces a saw-tooth voltage wave-form which is applied to the horizontal deflecting plates 25 to sweep the electron beam through the narrow band of light-sensitive material 18. The frequency of the saw-tooth wave-form is such that the electron beam is swept across the screen 17 once for each card column. A blanking voltage is applied to the grid 23 to blank the electron beam during the fly-back time in known manner. A pulse generator 29 is triggered at the beginning of each saw-tooth scanning voltage to initiate the generation of time indices or index pulses simultaneously with the beginning of each sweep of the beam of electrons across the screen. An electronic commutator 31 having one position for each column 12 of a card 9 is advanced one position by a signal from the scanning and blanking circuit at the end of each sweep of the electron beam so that the position of the commutator corresponding to the column 12 of the card appearing in front of the aperture 6 is active during the sweep through the image of that column. A number of electronic gates 33 equal to the number of the positions of the commutator are connected through a control panel 34. As successive positions of the commutator are turned on, successive gates are opened so that the gates 33 corresponding to the column 12 of a card modifying the light falling on the screen 17 will be open during the time the beam of electrons is swept through the image of the column. Signals produced at the output electrode 21 of the iconoscope corresponding to light passing through card perforations are fed to the amplifier 28. The amplified signal is fed to the shaping circuit 32 and thence to the pulse generator 29. The output index pulses from the pulse generator are fed over a common.lead 35 to all the gates 33 only one of which will pass the pulses corresponding to the particular column being sensed, the value of the perforation being represented by the number of index pulses passing through the gate. Electronic counters 36 may'be connected to the electronic gates 33 to receive the index pulses passing therethrough and store the data read from the cards 9. As the electronic commutator 31 is advanced through its last position a signal is fed back to the scanning and blanking circuit 26 to terminate its operation. The beam is then unblanked and held at A until the leading edge of the next card 9 crosses the aperture 6, at which time the operation described above is repeated.