Patent GB-595556-A (GB)
Title: Improvements in or relating to electrical item comparing system
IPC: G06F7/02
Filed: 1944-07-03
Abstract: 595,556. Electrical calculating- machines. INTERNATIONAL BUSINESS MACHINES CORPORATION. July 3, 1944, No. 12675. Convention date, April 17, 1943. [Class 106 (i)] [Also in Group XL] A cyclically operating system for comparing a pair of values manifested by electric signals differentially timed comprises a circuit controlled by the signals to produce pulses, a thermionic valve trigger circuit being operated by the pulses in such manner that the trigger circuit has one or another of two stable electrical states at a certain time in the cycle depending on whether the said values are equal or unequal. Two embodiments are described, the first in a record-controlled machine, the other in a manually settable machine or in a read-out commutator. Record-controlled machine. The record is marked on a film which continues to be fed past the sensing stations only so long as the classification data remains constant. Successive frames of a film F, Fig. 1, are marked with spots arranged in single point Hollerith numerical code and known alphabetical combinational code to form successive records. A motor M drives feed sprockets 55 through separate clutches of the type described in Specification 483,021, the clutches engaging only while the corresponding magnets 68 are energized, the film advancing one frame length for each tooth of a ratchet in the clutch mechanism. The film is scanned in a gate 77 at two sensing stations slightly less than a frame-length apart. Light from a source 86 passes through two quartz pieces 88, 89 to give a thin line of light at each sensing station. Light passing through the film in each denominational position enters quartz rods 84, 85 leading to corresponding upper or lower photo-cells UP, LP. In one machine cycle, the film advances one frame length consisting of fourteen cycle points. Trigger circuit. The circuit comprises a number of component trigger circuits of the type shown in Fig. 4, two triodes 164a, 164b being in parallel and having equal controlling resistances and condensers. Such a circuit has two conditions of stability, the first with tube 164b conducting and tube 164a at shut off, so that the potential of point 165b is high and the potential of point 165a is low, when the element enclosed in dashed lines is said to be on, and the reverse state when the element is said to be off. A positive pulse applied via condenser 167b to resistance 168b, when the element is off, will turn the element on, after which a positive pulse to resistance 168a will turn the element off. Similarly, a negative pulse applied to resistance 168b or 168a will turn the element off or on, respectively, if the element was previously in the reverse state. If the condensers 167a, 167b are connected in parallel, a pulse, whether positive or negative, will reverse the element. Operating circuit. Control pulses. A multivibrator W produces a series of sharp pulses, alternately positive and negative on a resistor 145, Fig. 6a, the pulses being shown in Fig. 7c. The positive pulses reduce the grid bias of a tube 146b, which is normally at shut off, to permit current flow therethrough so as to excite a resonant circuit comprising an inductance 147 and a condenser 148, the output of which is fed to an amplifier 151 having an output of sufficient power to drive the motor M when a switch 152 is closed. By this means, the film feed is synchronized with the control pulses generated by the multivibrator. The classification data is divided into major, intermediate and minor groups, each of two columns in the record, a change in any of the groups stopping the film feed. Fig. 6a shows only the circuit elements At, Au, Ax relating to the major classification group, but the elements of the other groups are essentially similar. Before operation, any of the elements T, At, Au, Ax, &c., which are on, are put into off status by successively reversing switches 195, 194 and 192 momentarily to discharge condensers 199, 198, 196 so as to apply positive pulses to the points 116a of the related elements. To start film feeding, the operator reverses switch 193 momentarily to discharge condenser 197 through resistance 162b to switch element T to on. The rise in potential of point 166b of element T renders tube 146a conductive and energizes the clutch magnets 68 to cause engage - ment of the clutch mechanisms and a ratchet drive of the film strip starts at time " D " of the next machine cycle. Comparison means. Each of the six photocells LP corresponding to the classification columns at the lower sensing station is connected to a tube in parallel with a tube connected to the corresponding photo-cell UP, the two tubes being connected to a common load resistor. Considering the cells LPt (Major) and UPt (Major) sensing the tens denomination of the major classification group, when LPt is illuminated, its impedance is low and the grid potential of the related tube L1At is high so that the tube is conducting. When the light is obscured by a spot on the film, Fig. 7e II, the impedance increases and the grid potential of tube falls so that the potential across load resistor 2At falls to apply a positive pulse to grids of element At, which is thus turned on as in Fig. 7g II. The lower sensing station is a fraction of an index point ahead of the upper sensing station with respect to like. designation spots on successive frames: If a matching designation is then sensed by the corresponding UP photocell, Fig. 7f II, the related tube U1At causes a second drop in potential across resistor 2At and the resultant positive pulse shifts element At back to off status. As the spots leave the sensing stations, after the midpoint of the cycle position, the potential drop across the load resistor increases in two steps to apply negative pulses to element At, which is again switched on and off, Fig. 7g II. If the designations in any one column do not agree, they will be sensed in different cycle portions so that the denomination element At will be turned on by the first spot sensed, Fig. 7e III, and stay on till that spot leaves the sensing station so that the element is on at the midindex point, Fig. 7g III. The operation of the element Au by the units order of the major group is similar to that of the element At. Points 166b of elements At, Au are connected to the grids of tubes 3At, 3Au, and when disagreement in the major group occurs so that either element At or Au is on and the related tube 3At or 3Au is conducting at the midindex point, it reduces the screen voltage of a pentode 5A to reduce current flow therethrough and raise the screen voltage of pentode 7A, the grid of which receives positive and negative pulses continuously from resistor 145. The tube 7A is normally at shut off but the coincidence of a raised screen voltage and a positive pulse at its grid at a mid-index point generates a positive pulse through the tube, and via condenser 163a applies a negative pulse to the grid of tube 164a of the class control element Ax to turn it on. Point 165b of element Ax is coupled by condensers and resistors to points 166b of the intermediate and minor control elements Bx, Cx (Fig. 6b, not shown), so that switching on Ax shifts Bx, Cx to on status also. Bx controls Cx in a similar manner. Interruption of feeding. Point 165b of element Cx is coupled via a condenser, resistance and line 211, to point 166a of element T, so that when element Cx is turned on, a positive pulse turns element T off, to reduce current flow through tube 146a so that clutch magnets 68 de-energize and film feed ends at time " D " of the next cycle. Neon tubes 212 glow when the class elements Ax, Bx, Cx are on, i.e. when there is a break in the related or higher classification group. To restart the feed and turn off the element Ax, Bx, Cx and related neon tubes, the operator reverses switch 194 momentarily. Element Cx, in turning off, applies a negative pulse to element T which turns on to re-energize the clutch magnets 68 so that feeding resumes at time " D " of the next cycle. The class elements Az, Bx, Cx may operate separate machine controls. When a blank frame is at the upper sensing station, disagreement is registered and feed stops. Modification. As opposed to the recordcontrolled machine just described in which agreement is manifest by continuing feed, in a modification comparing data represented by settable entry receiving and representing means, agreement is manifested by lighting a signal lamp. Trigger circuit. The circuit comprises a number of trigger circuit elements of the type shown in Fig. 5, the element comprising a left-hand and a righthand portion in parallel with equal controlling resistances and condensers. A portion is said to be on when its triode is conducting, the other triode being then at shut-off. With switches 175a, 175b open, positive pulses to resistors 173a, 173b switch the left or the right portion of the element on, if previously off. Negative pulses have no effect. Closing switch 175a or 175b renders pulses in the associated resistance ineffective. Electronic commutator. An electronic commutator of the type described in Specification 593,577, [Group XL], is employed to generate positive control pulses on resistors 9R ... OR, 11R, 12R, 9RR, 4RR at the appropriate times in the machine cycle. Negative pulses are also generated on these resistors at the times shown in Fig. 9. Ten pentodes 226(9) ... 226(0) have their suppressor grids connected to point 166b of element K2 which is normally off. The control grids tap resistors 9R .. OR. The tubes are at shut off except when the suppressor and grid potentials are concurrently high at the times, as described below, when element K2 is on. Comparing device. The operator closes the main switch and opens a switch 218 to start the electronic commutator, which is selfconditioning, in known manner. The two amounts to be compared are entered into devices F, G, Fig. 8