Patent GB-967786-A (GB)
Title: Improvements in character reader
Inventor: ECKERT ALTON BROOKS
IPC: G06K9/00
Filed: 1962-12-04
Abstract: 967,786. Automatic character reading. PITNEY-BOWES Inc. Dec. 4, 1962, No. 45830/62. Heading G4R. In a character reading apparatus of the kind in which a waveform derived by scanning the character is sampled in a tapped delay-line, pairs of the sample values are compared in a number of  comparators and the outputs are combined in a diode logical circuit to identify the character. The characters, which are specially shaped (Fig. 1), may be magnetic and passed under a magnetic head to derive the waveform or alternatively photoelectric sensing may be used. The waveform, Fig. 2 has peaks at spaced points along its length corresponding to the vertical lines between which lie the black parts of the character. The delay line tappings coincide with the peak points so, at the instant that the waveform is properly located in the delay-line, the relationship between the signals at selected pairs of tappings defines the waveform and consequently the character sensed. The tappings are connected in selected groups via cathode followers to the grids of comparator triodes 44, 45 Fig. 8. The difference signal is applied to a Schmitt trigger 51 which assumes one or the other state according to which of the inputs is the larger. The logical circuit consists of a number of diode AND gates Fig. 9 each adapted to respond to a particular group of conditions as indicated for the character "2". These circuits are enabled by a read pulse if certain conditions are satisfied. One of these is that there is a record present in the sensing position, another is that the waveform signal exceeds a certain noise level and the third is that there has been no recognition signal for a certain period of time. The presence of the record is detected photo-electrically.. The signal level is compared in a double triode with a noise level voltage and the output is used to set a trigger. The outputs from the recognition circuits are combined and applied to a threshold circuit which detects that a character has been recognised. This sets a blanking circuit which prevents another recognition operation taking place until the next character is due. False recognitions from the trailing parts of one waveform and the leading parts of the next are thereby avoided. Signals representing the three conditions are combined in a diode gate and used to generate the read pulse for all the recognition circuits. The combined outputs from the recognition circuits are also applied to a further threshold device which responds to an excessive signal such as would indicate that more than one recognition circuit had responded. Short spurious outputs from the recognition circuits are ignored by integrating circuits which need a signal of a certain duration to operate associated output triggers. The recognition signal may be applied to accounting or sorting apparatus. A "doubleread" signal may cause the record to be sorted into a reject pocket. In a modification, the compensate for light or heavy printing provision is made to recognise sets of early and late comparison signals. Light printing causes the positive peaks to arrive late and negative peaks to arrive early as shown in Fig. 18A. Heavy printing has the reverse effect. In the circuit of Fig. 19 some comparator outputs are connected to "Late" AND gates and some to "Early" AND gates. The resulting signals, after elimination of short spurious pulses are briefly stored on triggers and the outputs gated to give recognition signals as before.