Patent GB-773966-A (GB)
Title: Improvements in record carriers and apparatus for cooperation therewith
IPC: G06K1/12
Filed: 1955-04-14
Abstract: 773,966. Statistical apparatus. INTERNATIONAL BUSINESS MACHINES CORPORATION. April 14, 1955 [April 16, 1954], No. 10751/55. Class 106 (1). A record card or like carrier has value-indicating marks consisting of discrete areas each differently conditioned to effect predetermined electrical responses of differently varying intensity in a pick-up capable of producing such responses. As shown in Fig. 1, the card has successive rows of marks, each mark being a magnetized area of the kind shown in Fig. 2. The area of each mark is magnetically conditioned to produce in the pick-up electrical responses of progressively increasing intensity, the rate of increase being different for marks indicating different values. The magnetized marks are produced by subjecting the magnetizable cards in the recording apparatus to the action of recording heads wherein the impressed voltage is caused to build up to a maximum during the recording operation at a different rate for each numerical value or digit. As described in Specification 773,967, the cards are fed through the recording machine at uniform speed and the total recording time is the same in each case regardless of the rate of increase of voltage. The magnetic record marks are therefore different for each digit or value and effect different responses in the record reading machine corresponding in value with the differences in the rate of voltage increase. The record marks may be transparent areas on a carrier of film as shown in Fig. 6, these marks being read by moving the carrier past a light sensitive pick-up. Card-sensing and interpreting.-The cards are fed at uniform speed past sensing coils, one for each column. Each sensing coil has an A.C. voltage 503, Fig. 5, induced in it according to the impressed magnetization of the record mark, this voltage has a wave pattern increasing from zero to maximum as shown. Each coil is connected to an analyser section containing control means for a gate device through which a number of successive impulses corresponding to the digit value of the mark recorded on the card are transmitted to the computing sections of the machine. An impulse , generator working in conjunction with a chain stepping circuit supplies a predetermined number of impulses during the time the card takes to pass through one recording cycle, i.e. the width of each row on the card. The impulse generator includes a disc P, Fig. 4, bearing magnetic markings, which is rotated to produce a series of pulses 147 in a coil. The stepping circuit has eleven stages and once started moves from one stage to the next as successive pulses 147 are received. The gate device opens when the voltage induced in the sensing coil approaches its maximum. Pulses 147 corresponding to the remaining stepping circuit stages are then transmitted to a counter or accumulator which counts the pulses passing through the gate to indicate the value of the record mark. In the case illustrated in Fig. 5 there are seven pulses during the time between the attainment of maximum voltage and the end of the stepping circuit cycle. This wave pattern accordingly corresponds to digit 7. Analyser circuit.-As shown in Fig. 4, the sensing coil is connected through transformer 501 and push-pull amplifier consisting of triodes 204, 206. The amplifier output is connected through transformer 208 to a double diode full-wave rectifier comprising diodes 210, 212 and a D.C. voltage, corresponding to the wave pattern is caused to appear in resistor 214. This voltage is amplified in a D.C. linear amplifier comprising pentodes 216, 218 and when amplified appears across resistor 219. The form of this voltage, which is negative, is shown at 504 in Fig. 5. The grid of a sharp cut-off triode 251 is connected to the junction of a potential divider connected between anode of pentode 218 and a suitable bias supply 221. Triode 251 is normally conductive when there is no signal on the sensing coil 202 but as soon as a small voltage is detected triode 251 becomes non-conductive. The triodes corresponding to all sensing coils are connected to a common line 250 so that when all the triodes have been made non-conductive the potential of this line rises. A positive pulse from this line is transmitted through condenser 310 to grid of triode 312 causing it to conduct and switch trigger Z from its " off " to its " on " state. The next pulse 147 after trigger Z has been switched on is inverted in transformer 512 and transmitted through condenser 514 to grid of triode 304 causing cut-off of this triode and a positive pulse to appear at point 516. This pulse causes momentary conduction of triode 518 and switches the trigger Z off. When trigger Z switches off, triggers W and Y (not shown), are switched on. Trigger W is switched off again by the next pulse 147, as shown in Fig. 5, and starts the stepping circuit by switching on the " 9 " stage. The stepping circuit advances- " 8," " 7," " 6," &c. by successive pulses 147, each stage being turned " on " by the turning "off" of the preceding stage. The trigger Y controls a " leveller " circuit correcting for irregularities in recording a misalignment of card feeding. The output of pentode 218 (D.C. voltage as at 504 in Fig. 5) is applied to the leveller circuit through a condenser 220. A voltage having the same rate of change as the voltage from pentode 218 is superimposed on a fixed base voltage in the leveller so that early or late card registration has no further effect. The leveller output 530 (Fig. 5), is applied across resistor 225 and is compared with a fixed standard voltage 532 (Fig. 5), determined by potentiometer 533 in a circuit comprising thyratron 226 and triode 228. The thyratron fires when the voltage of point 531 becomes sufficiently negative. The output from this comparing circuit is in the form of an impulse, produced by the firing of the thyratron the timing of the impulse in the record cycle being the indication of the rate of increase of the wave pattern of the record mark. The positive pulse from the thyratron is transmitted through condenser 232 to the grid of triode 234, thereby switching on a trigger comprised of a double triode 236. While this trigger is on it maintains open the gate device which consists of pentode 238. The input pulses 147 can then be transmitted through triode 321 and line 242 to the output terminal 240 of the analyser section. This terminal is connected to the counter unit of the machine as stated above, the counter indicating the value of the record mark by counting the pulses passed through the gate device. Photographic records.-When the records are marks in the form shown in Fig. 6 on a film carrier, the marks are sensed by an apparatus shown diagrammatically in Fig. 7. The film F comes from supply reel 8 under pulley 10 over sprocket 11 under pulley 12 and to takeup reel 7. The sprocket 11 consists of a roller on one side and a toothed wheel on the other engaging the side perforations of the film but leaving the space beneath the centre of the film clear. The toothed wheel is driven so that the film is moved in a curved path round sprocket 11. Light from an arc lamp 18 is projected in a line through the film, through a projection lens 180 and through the slit 20 in a mask 19 on to a photo-electric cell 26. The quantity of light received in the cell depends on the position of the projected image with respect to the slit as shown in Fig. 8. As the image moves in the direction of the arrow the amount of light passing into the cell will increase at a rate which represents the digit value. Another light source co-operates with photo-electric cell 25 to sense the film at a second position. There is one photo-electric cell 25 and one photo-electric cell 26 for each column of images on the film. The output from the photoelectric cells are used to control an interpreting apparatus similar to that described for use with magnetic record marks. An impedance transformer in the form of a cathode follower is used, the output from the cathode follower being amplified and applied to the grid of pentode 216 (as in Fig. 4).