Patent GB-595555-A (GB)
Title: Improvements in or relating to accumulating apparatus
IPC: G06F3/153
Filed: 1944-05-16
Abstract: 595,555. Electrical calculating-apparatus. INTERNATIONAL BUSINESS MACHINES CORPORATION. May 16, 1944, No. 9408. Convention date, May 23, 1941. [Class 106 (i)] [Also in Group XL] A hard valve accumulator has a source of electrical impulses for sequentially switching conditioned trigger units of a hard valve register, entry controlling means causing as many impulses to be applied to the register as represents a digit being added, each register comprising trigger units less in number than the radix interconnected in a ring, each trigger unit having two stable states and being interconnected conductively to the succeeding trigger unit so that a unit conditions a succeeding unit for switching at a subsequent impulse, any digit being represented by the combination of the trigger units in the ring in one or other of their two stable states. Similar parts are indicated by like references throughout the circuits. Trigger circuits. The main circuit is built up of a number of trigger circuit units operating in the manner described in Specification 595,553 (Figs. 1 and 2, not shown). The units are divided into two portions, one or other of which is on according to whether the potential of a point 66a or 66b in that portion is high, neon tubes 78 indicating which portion is on. Basic circuit. The principles of the electronic commutator and the accumulator are illustrated in Fig. 3. Throe trigger units S1, S2, S3 are arranged so that, starting with the right-hand portion of S1 on, so that the screen potential of tube 69b (S2r) is high, and the other righthand portions S2r, S3r off, a positive pulse from resistor 72 tube 69b (S2r) conducting and so trips S2r to on. The next pulse turns S3r on. S3r then conditions S1l so that succeeding pulses turn on S1l, S2l, S3l, S1r, S2r and so on. Electronic commutator. A machine cycle is divided into ten portions called index points D (or O), 9, 8 ... 1 and the frequency of the oscillator and amplifiers of a multivibrator is such that there is one cycle for each index point. As described in Specification 595,554 (see Group XL), the multivibrator comprises tubes 83a, 83b, 91, 92 and feeds sharp pulses to resistors 98, 72, the pulses being of the type shown in Figs. 6d, 6c, respectively, and called b-phased and a-phased. Resistor 72 feeds a continuously operating electronic commutator, Figs. 5a, 5g, of the type shown in Fig. 3. The potentials of the points 66a, 66b of the units making up the commutator thus rise and fall once in each cycle to produce sharp positive and negative pulses on resistors 104a-j, Fig. 5g, and 104k, l, m, Fig. 5h. The resistors 104a-j feed the grids of tubes 293a-j, the normal grid bias of which is zero. The positive pulses therefore have no effect, but the negative pulses decrease current flow to produce positive pulses on lines 114, 105b-j at times D, 9, 8 ... 1 in each machine cycle as shown in full lines in Fig. 8. As described later, the " 9 " to " 1 " pulses on lines 105b-j are used as digit manifesting pulses, the '' 0 " pulse on line 114 terminates entry operations in addition, the " 0 '' pulse on resistor 104l initiates or terminates single entry control, the " 1 " pulse on resistor 104k is for fugitive one entry and for terminating the manually controlled part of the single entry control, and the " 9 " pulse on resistor 104m is used to initiate subtraction. Entry control device. The tens order of the accumulator and its entry control device are described as being typical of the others. The entry control device Et, Fig. 5d, is turned on, in additive operations, by a pulse representative of the digit to be entered and thereupon permits advancing pulses equal in number to the value of the entry to be effective in turning on its associated digit manifesting portions sequentially. Et is similar to the unit shown in Fig. 1 except that pentode 69a is replaced by a triode 116. The device Et is normally off, but as described later under the heading " Operation " can be conditioned for turning on by having the screen potential of tube 69b raised so that the receipt of a digit-representing pulse over the appropriate line 105b-j, the appropriate contacts 117t, condenser 296b and resistor 297b, at a differential time in the cycle, reduces the negative grid bias of tube 69b (Et) to raise the potential of point 66b and turn the device on. This raises the screen potential of tube 119a, the control grid of which receives b-phased pulses continuously from resistor 98, Fig. 5a, so that through condensers 122a, 122b a-phased negative pulses appear on resistors 123a, Fig. 5d, and 123b, Fig. 5j, the accompanying positive pulses being attenuated by a connection to the grid of tube 119b. The negative pulses on resistor 123a, however, reduce the current flow through tube 119b so that b-phased positive pulses appear on resistors 72a, 72b, Fig. 5d, the number of pulses corresponding to the digit to be entered and a lag of half an index point existing between the turning on of the entry control device and the production of the pulses. A " 0 " pulse on line 114 to tube 116 shuts off the unit Et to stop production of further pulses on resistors 72a, 72b and 123b. Digit manifesting units. The tens order of the accumulator comprises five units At5-0, At6-1 ... At9-4, each unit comprising a right and a left portion. The accumulator indicates zero when At5-0r, i.e. the right-hand side of At5-0 is on and the other right portions are off. As described with reference to Fig. 3, successive pulses on resistors 72a, 72b turn on the right portions sequentially and then the left. Carry-effecting device. Carry may take place at any index point in a cycle, the advancing pulses on resistors 72a, 72b being at midindex points and the carry pulses on resistor 123b being half an index point earlier so that no interference takes place. Because the screen potential of tube 119a is still rising when the entry control device is turned on in addition, the first pulse to its grid does not produce a pulse on resistor 123b and supplemental means are therefore provided. With switch 191b open, Fig. 5b, the screen potential of tube 303, Fig. 5j, is high. When Et is turned on, the potential of point 66a falls to increase momentarily the grid bias of tube 303, reducing current flow therethrough, condenser 307 charges and a positive pulse appears on resistor 123b. Carry is effected by tube 130a, the screen potential of which is high when portion At5-0l is on and the suppressor grid potential is high when portion At9-4l is on. Thus, when the tens order stands at 9, the receipt of a positive pulse on the control grid from resistor 123b, which pulse precedes an advancing pulse on resistors 72a, 72b by half an index point, increases current flow through the tube 130a, to apply a negative pulse to tube 134 which, via line 153b and condenser 125b, produces a positive pulse on the resistors 72a, 72b of the hundreds order to add one in that order. Tube 134 also produces a positive pulse on resistor 137, Fig. 5j, used in simultaneous carry. If the tens order is at 9 when carry takes place from the units order, so that a carry pulse on resistors 72a, 72b advances the tens order to 0, the switching on of At5-0r raises the screen potential of tube 130b, Fig. 5j, momentarily. At the same time, the pulse from resistor 137 of the units order reduces the negative grid bias of tube 130b and, via tube 134, produces a carry pulse on the resistors 72a, 72b of the hundreds order. Operation. Addition. The operator opens switch 101, Fig. 5a, to permit operation of the electronic commutator. The other switches are as shown. As described later, the accumulator is zeroized. The machine has a full keyboard, the items being set up to close the appropriate contacts 117, Fig. 5h, and a motor bar is operated for each entry to depress switch 181m, b, Fig. 5b, to connect a charged condenser 194 to resistance 195, which therefore receives a single pulse and turns on element T1 at any point in the machine cycle. T1 conditions T2 so that the next " D " pulse from resistor 104l turns on T2, which raises the screen potentials of tubes 69b in the entry control devices to condition them for turning on at differential times during the entry cycle on the receipt of pulses from the appropriate lines 105b-j. A " 1 " pulse from resistor 104k to tube 69a turns off T1 so as to condition T2 for turning off at the receipt of the next " D " pulse, the entry control devices are thus turned off and entry ceases after only one cycle. Further entries are made in a similar manner, carry taking place in the manner already described. Subtraction. Instead of entry into an order of the accumulator beginning at a differential time in the cycle and ending at " D " in subtraction, the entry control device is turned un at time " ¢ after D " and off at the time corresponding to the digit to be subtracted, whereby the nines-complement of the subtrahend is entered. The subtraction of 3 from the units order and 0 from the tens order is illustrated in Figs. 14-16c (3). Switch 191a, Fig. 5b, is reversed and switch 191b is closed, the latter reducing the screen voltage of tube 303, Fig. 5j, so that the supplemental means for the generation of the first carry pulse on resistor 123b is rendered inoperative. Keys are set and the motor bar depressed as in addition, and when T2 is turned on, the screen potential of tubes 139a and 69b (T3) is raised. A large " 0 " pulse from resistor 104l turns on T3, despite the fact that the screen voltage has not reached full value, concurrently with T2 (Figs. 14b, c). The grid of tube 69a (T3) receives a " 9 " pulse from resistor 104m tu turn off T3 after one-tenth of a cycle. While on, T3 conditions tube 140a so that one of a series of positive b-phased pulses to tube 140a produces a single negative pulse which is applied to the grid of tube 140b, which sends a " ¢ after D " pulse to turn on the entry control devices, w