Patent GB-542927-A (GB)
Title: Improvements in or relating to calculating and statistical machines
IPC: G06F7/491
Filed: 1940-07-23
Abstract: 542,927. Calculating-apparatus. BRITISH TABULATING MACHINE CO., Ltd., (International Business Machines Corporation). July 23, 1940, No. 12075. [Class 106 (i)] An electrical apparatus comprises an accumulator constituted by an oscillating valve circuit, a valve circuit for effecting a digital entry, and means controlled thereby for controlling the oscillating valve circuit to represent the digit by determining its phase. The oscillating valve circuit includes a condenser and is adapted to oscillate normally at a constant frequency by periodic discharge of the condenser and includes means for altering the phase of the discharge by altering the rate of charge of the condenser for a period sufficient to alter the phase by the desired amount. A three denominational adding device is described comprising relaxation oscillators serving as accumulator elements, frequency changing elements, positive pulse emitters, sets of digital contacts, transfer circuit elements, synchronizing oscillators, and resetting circuit elements. An accumulator element is shown in Fig. 1 in the form of a relaxation oscillator comprising a discharge valve 21, a condenser 22, a pentode valve 23 and various resistances 20, 23a, 24a, 24b, 25a and 25b across the mains supply 1, 2. For a given control grid bias, the current through the pentode is substantially constant over a wide range of anode potential so that the rise of voltage across the condenser is substantially linear with respect to time ; the charging and discharging of the condenser thus produces. an oscillatory current of sawtoothed form which can be exhibited on the screen of a cathode ray tube and by the use of a mask 89 as shown in Fig. 10 can serve to indicate a digit by its phase. These images may be recorded on a record card photographically. The phase is changed by altering the rate of charge of the condenser by varying the screen voltage in the pentode by means of the circuit arrangement shown in Fig. 3. When a positive potential is applied to the line 28c the negative grid bias of the valve 28 is reduced and more current flows through the valve to reduce the negative grid bias on the valve 26. Current through the valve 26 raises the potential at point 24 to double the frequency of the oscillator Fig. 1. The potential at point 24 is returned to normal by applying a positive potential to the line 27c which reduces the negative grid bias on valve 27 'and passes more current to lower the potential at point 27b to extinguish valve 26. In this manner digits are entered in accordance with the number of divisions in the cycle of operation between the application of potential to the lines 28c, 27c. The relaxation oscillators operate normally at a constant frequency of two cycles per machine cycle. In the device other pulse oscillators, Fig. 4, are provided to operate at a frequency of one cycle per machine cycle. There is a single pulse oscillator for each digit 1 to 9 adjusted to operate at the corresponding phase and arranged to convert the negative pulse of voltage applied to the point 20a of the circuit into a positive pulse at the point 31a. Other positive pulse emitters are arranged to emit positive pulses at the points in the cycle represented by D, D¢, 11, 12 and O. These emitters are represented as rectangles in the circuit diagrams, Figs. 5 and 6. The pulse emitters 1-9 are connected through grid bias batteries 35 and a cable 34 to three sets of contacts 1-9 for the three denominations. The closure of the contacts by keys, punched record cards, photo-electric cells, or otherwise in the units, tens and hundreds denominations, connects the emitters to pentodes 28u, 38t and 38h respectively, and the positive pulses emitted reduce the negative bias on their control grids. After the number has been set up a switch 46 is operated momentarily to close contacts 46b which causes a condenser 48 to discharge. This action reduces the grid bias of the valve 50 and current passes to raise the potential of the screen grid of pentode 45 which passes current to reduce the negative bias on grid of valve 52. The current flow through valve 52 raises the potential at point 53a and through the lines 55 raises the screen grid potential of pentodes 51, 38u, 38t and 38h. When the control grid bias is reduced and the screen grid potential is raised these pentodes pass more current and in association with the valves 41u, 41t and 41h emit positive pulses to the lines 28cu, 28ct and 28ch which are connected to the circuits described with respect to Fig. 3 and Fig. 1. The accumulator elements thus change their phase in accordance with the digits entered by doubling the frequency at the appropriate cycle divisions and by stopping the double frequency period at the "O" position. This stopping is effected by the positive pulse emitter O, Fig. 5, which is connected at the point 33a through a battery 35 to the lines 27cu, 27ct and 27ch to the grid of the valve 27, Fig. 3. The emitter O is associated with a valve 56 whereby another positive pulse is emitted to reduce the negative bias on the control grid of pentode 51 and return the screen grid of pentode 45 to its normal low value. This action is controlled by the emission of a positive pulse at point 11 and by the valves 50, 52, and 54 and all circuits are then back to normal with the relaxation oscillators at phases corresponding to the digits entered. Subtraction may be effected by the known method of adding the complement. Transfer operations.-Whenever in the cycle an accumulator element discharges twice a transfer condition is set up which at the following point " 11" in the cycle causes the element of higher denomination to oscillate at double frequency while at the following point " 12 " normal frequency is resumed. The circuit arengagement for effecting this carry over is shown in Fig. 6; the upper half represents the connections to the accumulator element AEu for the units and the lower half those for the tens denomination AEt. The effect of successive discharges of AEu is alternately, to raise and lower the potential at point 66u and since the screen grid of pentode 67u is connected to that point transfer depends on the grid being at a high potential at point "11" in the cvcle. The positive pulse from emitter 11 reduces the control grid bias or pentode 67u and if, at that moment, the screen grid potential is high the valve passes more current and sends a pulse from the point 68au to the line 28ct in the tens denomination. At the following point " 12 " in the cycle a pulse is sent by the emitter 12 through the battery 70 to the line 27ct to cause the tens accumulator element to resume its normal frequency thus adding one. Subsequent or long transfers are provided for by the provision of a pentode 71t in parallel with the pentode 67t and connected to the points 33at and 68au. At point " 11 " in the cycle pentode 67t sends a pulse at point 68at to the line 28ch for the hundreds denomination, normal frequency being resumed at the point " 12 in the cycle. The correct sequence of rises and falls of potential is provided for by valves 73u, 73t associated with a pulse emitter D¢. Re-setting operation.-The re-setting of the accumulator elements to zero is effected by closing switches 78, 79, Fig. 5, and by means of the circuit arrangement shown in Fig. 9. The O emitter sends a negative pulse to the valve 80 which converts it to a positive pulse at the point 81 which point is connected to the grids of valves 82u, 82t and 82h in parallel with the valves 28, Fig. 3, of the accumulator units and thus doubles their frequencies. The switch 79 sends a positive pulse by the emitter 11 to the lines 27cu &c. and the frequency of the units returns to normal. The point 21a in each unit is connected through a condenser 83u to the grid of a valve 84u and each unit acts as a pulse emitter so that digits are added successively to the units until they reach zero. Synchronizing arrangements.-All the continuously operating oscillators are synchronized by means of a main oscillator and intermediate oscillators, Fig. 8 (not shown) discharging at different phases.