Patent GB-973064-A (GB)
Title: Improvements in method of coding documents and apparatus for reading them
Inventor: ECKERT ALTON BROOKS
IPC: G06V30/224
Filed: 1963-01-29
Abstract: 973,064. Statistical records. PITNEY-BOWES Inc. Jan. 29, 1963, No 3615/63. Heading G4M. A record document Fig. 2 has data recorded on it by printing a full group of characters 0-9 and obliterating at least one of the characters, sensing means and other circuitry being provided to identify the obliterated character. The characters in "post-coded field" are of such a design that except for "1" they all produce the same waveform when scanned so that they all produce a signal on the " 2" lead 14, Fig. 1. Character "1" produces a signal on the "1" lead 13 and dividing marks 10 produce responses on lead 22. These three leads are connected via an Or gate 23 to a character counter 24 operating in binary scale. As the characters pass under the sensing head they are counted; after character "1" has been sensed the counter has a count of 2. If the character "2" is obliterated or multilated so that it does not give a recognition response a circuit 25 detects the gap and opens gates 45 allowing the contents of the counter to pass to store 50. The output of this store is applied to a recoder 55 to give a signal on the appropriate one of ten leads 57. The gap detector consists of a capacitor which is discharged by each character pulse and which is charged at a constant rate between pulses such that where characters are recognised successively the capacitor is discharged before it can reach a certain threshold level. If a character is obliterated the capacitor charges through the period of the gap and exceeds the threshold level giving a gating signal on line 78. Gap signals are counted in counter 31 so that if there are no gaps or more than one, the recoder 55 may be inhibited. A gap signal causes the counter 31 to apply a signal on line 68 but any other condition removes this signal. A circuit 26 detects the occurrence of a double gap, the arrangement being the same as for circuit 25 using a suitably lengthened charge time. If this circuit responds, the signal is removed from lead 71. At the end of the group the detection of the "end-of-group" symbol 10 causes line 22 to pass a signal through gate 56 and enable recoder 55. If there have been more than one missing character, or none,the gate remains closed. A reset circuit 58 is also energized by the signal on lead 22 to reset counters 24 and 31 and store 50. Circuit 58 is dependent upon a "document present" signal on lead 59. In the form of Fig. 7 the characters are shaped so that they are each properly recognised, except the one that has been obliterated and corresponding signals are produced successively on leads 83-92; the converter 101 converts the input to binary scale giving a number one higher than the input. An input of "1" gives an output of "2". When a character is recognised a signal on lead 94 passes through Or gate 107 and over lead 109 to counter 98. Gap detector 119 detects a missing or obliterated character and produces a signal which also passes to counter 98. The value in counter 98 and the output of recoder 101 are compared at 106. If the " 2" is obliterated there is no output from converter 101 while counter 98 has a count of three. A mismatch signal is produced on lead 118 to open gate 123 allowing the missing character signal, delayed in delay 124 to pass to gates 129 and to missing character counter 100. The value in counter 98 is thereby transferred to converter 130 to give a signal on one of ten output leads corresponding to a number one lower than the input number so that the count of three gives an output on the " 2" lead. As before the converter 130 is enabled through gate 131 if the missing character counter 100 has counted only one and if the double gap detector 120 has given no output when the end-ofgroup signal arrives on lead 95. If a double recognition results from reading a character, a signal is produced on lead 93. This passes through the gate 93 in the same way as a mis-match signal 118, resulting from a misrecognition by the reader 82. The character counter therefore counts all characters whether correctly or incorrectly recognised or giving a double recognition. In the form of Fig. 8 the character signals, as they are generated, reset triggers 140-143, the obliterated character leaving the corresponding trigger set. The end-of-group signal on lead 139 passes through gate 145 to enable the gates 156-159 giving an output on the corresponding lead. If more than one character is missing the circuit 151 connected to each trigger by adding resistors 146-149 closes gate 145 and prevents readout. The end-of-group signal on lead 139 is also differentiated at 144 and resets all the triggers. Instead of a single obliterated character, there may be a combination of obliterated characters representing the desired data. The circuit of Fig. 8 may be adapted to respond to such a combination. In the form of Fig. 9 the characters all produce signals on lead 163 which step a shift register 164-170 so that at the end of a group one of the stages should be different from the others. The gates 177-182 are opened by the end-of-group signal provided no double recognition signal is detected by circuit 183. The character signals pass over lead 172, gate 171 and delay 173 to the shift pulse generator 174. When the obliterated character is read the gap detector 175 gives a pulse as before which passes through the gate 171 to give a shift pulse in the same way as a character. In another form there are two shift registers, the character signals being divided between them. A ten-input AND gate connected to suitable outputs of the register stages detect when all ten characters of a group have been recognised the gate responds giving a read-out pulse. The necessity for an end-of-group character is thereby avoided. Instead of using characters, symbols may be used as in Fig. 11 which are the same and which are complicated enough to prevent a recognition response from spurious pulses. Specification 967, 786 is referred to.