Patent GB-883965-A (GB)
Title: A method and apparatus for printing and reading
IPC: G06V30/224
Filed: 1959-10-16
Abstract: 883,965. Sensing records; automatic character reading. SPERRY RAND CORPORATION. Oct. 16, 1959 [Oct. 16, 1958], No. 35169/59. Class 106 (1). Data is recorded on a record by printing legible characters each with at least one additional mark to provide a distinctive array of elements which can be sensed magnetically to produce characteristic electric signals. The character and the additional mark may be both magnetic as shown in Fig. 1d. The waveforms produced by sensing with a magnetic head an " 8 " and an " H " are very similar but with the addition of differently placed additional marks sufficiently different waveforms are produced as shown in Fig. le. These may be rendered into binary form as indicated in Fig. 1f. In the form of Fig. 2 only the bar-like marks beneath the character are sensed, the printing being effected by a single type face through two ink ribbons, the lower one only being magnetic. The marks may be alternately vertically staggered to avoid indefinite signals due to the spreading of ink between the marks. In the form of Fig. 4, the marks are above the character and both are printed in magnetic ink. Sensing devices 24, 25 sense the characters and associated groups of marks respec - tively. The characters are specially shaped so as to induce in head 24 a clear start pulse to initiate the sensing cycle of the bar marks, all six positions of which can therefore be used for data. In the form of Fig. 2, the first position is used as a start mark leaving only five positions for data. After being printed the characters are magnetized and sensed by being passed under a magnetic reading head. Sensing.-The record 50, Fig. 9, is sensed by a magnetic head 51 and the signals amplified at 52 to give signals shown at A in Fig. 11. A voltage discriminator 53 produces a square wave which after amplification at 54 and shaping at 55 is as shown at B in Fig. 11. After differentiation at 56, the peaked wave C is obtained, the negative peak being eliminated by clipper 57. The resulting positive pulses are applied to a delay unit 58 and a pulse generator 59, the output of which consists of a pulse occupying about 80% of a bit time. The output from generator 59 passes to another generator 60 the output of which occupies 20% of a bit time. The two pulses are combined in a mixer 61 to produce a pulse lasting approximately for a full bit time. The use of two generators allows resetting in the case where two adjacent " 1 " 's occur. This full bit time pulse opens a gate 62 to allow pulses from a source of clock pulses to pass to the utilization device 65. The delay 58 delays the positive peak pulse from clipper 57 so that it occurs at about the mid-position of the bit time. The start mark produces a start pulse which having passed through the delay 58 starts a clock pulse source 64. This is stopped after six pulses have been counted in counter 66. If the arrangement is as shown in Fig. 4, the start pulse which is applied to start the clock is derived from the character senser 24 through a chain similar to that 52-57. While the signals from mark senser 25 are applied to pulse generator 59.