Electronic apparatus for reading symbols

850,582. Automatic character reading. SOLARTRON ELECTRONIC GROUP Ltd. March 25, 1957 [March 29, 1956], No. 10010/56. Class 106 (1). Apparatus for reading symbols derives signals from elementary areas, applies them to binary storage devices which are set into one condition or the other according to the density or state of the elementary area; input leads from the devices being connected through logical elements to output leads representing the different symbols to be read, a predetermined voltage condition arising from the setting of the storage devices corresponding to the symbol being read. A flying spot scanner 20 with line and frame deflectors 21, 22 scans in vertical lines the black symbols on a white paper background 26. The signals generated by photo-cell 28 pass through clipper 33 to bi-stable storage devices 30 e.g. electronic triggers, ferrite cores or capacitor store devices. The o and x states apply respective negative potentials to output leads 31, 32. In the case of sensing numerals 0-9 there are one hundred devices 30 and two hundred leads 31, 32 and the latter are connected to the leads 34 of the output terminals through logical elements 35 according to the scanning code for the symbols. A mechanical switch distributer or electronic switch 38 applies a negative voltage to the leads 37 in succession, and a black scan signal applied simultaneously causes its storage device 30 to assume its x state. A suitable electronic switch 38 comprises two shift registers, one for units and one for tens, each comprising a cascade of trigger circuits (Figs. 6 and 7, not shown), the leads of the two cascades being interconnected through diodes. The unit register passes a negative signal at each step, the pulse at 9 resetting the unit register synchronizing the scan' and passing a pulse to the tens register. As shown in Fig. 5, non-uniformity of the scanning spot is compensated by an auxiliary photo-cell 58 receiving light from the scanning spot direct and connected through an amplifier to the grid of the C.R.T. 20. The scanning spot may have a high-frequency "wobble." Centring errors in the symbol are accommodated by adding conditions representing possible slight displacement. In a modified form of storage device 30 Fig. 14, a transistor 68 controlled by " and " circuits fed by the signals from the electronic switch lead 37 and the photo-cell 28 through diodes 70, 71 respectively, governs the charging of a condenser 75 which is discharged when a positive pul