Patent GB-786051-A (GB)
Title: Improvements in or relating to electric calculators
IPC: G11C11/23
Filed: 1950-06-23
Abstract: 786,051. Electric digital-data-calculating apparatus. DIRKS, G. June 23, 1950 [Oct. 1, 1948], No. 37233/54. Divided out of 786,021. Class 106 (1). Electrical calculating apparatus includes means for producing a cathoderay beam, a screen with a first group of result areas representing a series of digits and a second group representing the same digits together with a carry, means for positioning the cathode-ray beam to select a result area in accordance with a computation, and means for scanning the beam over the selected result area to generate a timed digit-representing signal and, if over the second group, a carry signal. As described, two double-beam C.R.T's are employed, one tube 56, Fig. 3, being used as a control tube for the computer tube 43, Fig. 1. Input and output means comprise multi-track magnetic tapes. Synchronizing signals picked up from one track of a first magnetic tape 65 by a head 158 are amplified and applied to a phase-shifting network to give waveforms which, applied to the X and Y-plates 57, 58, respectively, controlling the C.R. beam 75, Fig. 3, cause a circular scan over secondary emission areas 109, 110, 111 ... 170 of the screen, Fig. 4, in synchronism with the sensing of the tape. At the beginning of the first quadrant of the circular scan the impingement of the beam on a target element 110 causes a signal at a terminal q, Fig. 7a, which fires a gas tube 94 and raises the screen potential of a pentode 83 to start a constant-current charging of a capacitor 89a. Arrival of the beam on an element 115, Fig. 4, causes a signal at terminal n, Fig. 7a, which, after amplification, fires a gas tube 89 and discharges the capacitor 89a. A similar sequence occurs during each 90 degree movement of the beam 75 and the saw-toothed waveform available at the anode of valve 83 is applied to the X- plates 44 and 46, Fig. 1, controlling a " sensing " beam 99 and "recording beam 135 respectively of the computing C.R.T.43. The Y-plates 47 of beam 135 and 60 of beam 76, Fig. 3, are subjected to a stepped waveform derived from a self-extinguishing gas tube 93, Fig. 7a, which is fired each time the beam 75, Fig. 3, passes over the element 109 (sensing- switch 126<SP>3</SP>, Fig. 7a, in position shown). During each brief period of conduction of tube 93, a constant-current pentode 81 steps up the charge on a capacitor 85 across which the stepped Y-scan waveform is developed. The beam 76, Fig. 3, is thus moved step-by-step over a column of targets 1251 to 125<SP>101</SP> in one hundred rotations of the beam 75, and when target 125<SP>101</SP> is reached the signal developed is applied to terminal e, Fig. 7a, firing a gas tube 88, discharging the capacitor 85, and thus restoring the Y-scan to its initial condition. Instead of a single column of one hundred steps, four-column and other arrangements are mentioned, controlled by a further group of targets (Fig. 4b, not shown). Transfer of digits from tape to C.R.T. The value of a digit signal is represented by its position on the magnetic track relative to a datum signal as described in Specification 786,034. The arrival of the circular scanning beam 75 at target element 116, Fig. 4, may be used as a corresponding datum, the resulting signal at terminal f raising the control grid voltage of an amplifier 78 whose screen grid has just been raised by the firing of a gas tube 90 by a signal from target element 115. The amplified signal fires a gas tube 91 whereby current starts to flow through a constantcurrent pentode 79 to charge a capacitor 84 until the digit signal, picked up from the tape by a head 69 and amplified by a valve 80, fires a gas tube 92 which increases the current in the cathode load of the pentode 79 and cut off the charging current. The voltage across capacitor 84 now represents the sensed digit and determines the vertical deflection of the beam 99. As the beam 99 is scanned horizontally on a line selected by the sensed digit in synchronism with the horizontal movement of the beam 135 which is to record the digit on the screen, it first passes a vertical datum element 22, Fig. 2, which causes a signal at the grid of a pentode 139, Fig. 7a, which after amplification, operates through a transformer 141 to brighten the recording beam 135 and so record a corresponding datum mark in the recording area 50. Similarly, the arrival of the beam 99 at an element 19n in the area 53 causes a corresponding recording in the area 50 which represents the digit sensed. in the magnetic tape. As the recording beam 135 moves to successive horizontal lines under control of the step-bystep charging of the capacitor 85, successive digits from the magnetic tape are recorded on the C.R.T. screen. Computation is performed by reading out in the second quadrant of successive cycles of the beam 75 the digits recorded in the area 50, each read-out being used to control the charging of capacitor 84 and being followed, in the third quadrant, by read-in of a corresponding digit from the magnetic tape. Thus, computation of a single denomination occupies one cycle of rotation of the cathode-ray beam 75. During the first quadrant or sub-cycle, as the beam moves between target elements 170 and 115, a carry, if any, resulting from computation in the preceding denomination will be recorded as described below. During the second quadrant, the charge on the capacitor 84, and therefore the vertical position of the beam 99, is raised in proportion to the value of the digit read from the area 50. The zero mark is recorded in the area 50 with approximately half the charge density of the digit mark and the operating potentials are such that only the pentode 78 produces sufficient output to fire the gas tube 91 when the zero mark is sensed. The capacitor 84 starts charging at a constant rate until a larger signal from the full-density digit mark fires a gas tube 92 via a pentode 80 and cuts off the flow through pentode 79. In the case of a recorded zero both tubes 91 and 92 are fired simultaneously upon detection of a full-density mark in the zero position, and therefroe no charge is given to the capacitor 84. During movement of the beam 75 through the third quadrant, the second digit, which is to be added, is sensed from the magnetic tape and causes further current to flow through the pentode for a time proportionate to its value. The charge on the capacitor 84 will then reach a value representing the sum of an initial carry (if any) plus the first digit, plus the second digit. The recording of the result digit in the second magnetic tape takes place during the fourth quadrant or sub-cycle of beam 75, and if the charge on the capacitor 84 has exceeded nine steps the vertical deflection of the sensing beam 99 brings it into the range of target elements 19<SP>0</SP> ... 19<SP>9</SP> and a " carry " element 21 which is connected to the trigger element of a gas tube 90. Thus, in the event of a " carry," the next cycle of the beam 75 starts with the gas tube 90 in a condition which allows conduction in the pentode 78 when the beam 75 falls on target element 111. This is terminated when the beam falls on the next target 112 and, via terminal g and amplifier 80 fires the gas tube 92 which cuts off the pentode 79 after the charge on capacitor 84 has been increased by unity. Subtraction is performed by changing over a switch 106 whereby the digits of the second number are entered in complementary form. There is provision for dealing with the " fugitive one ". The result of the computation may be recorded on a second tape, together with a synchronizing track read from the first tape, by feeding the signals detected by a pick-up plate, as the sensing beam is scanned over the result area, to the grid of an amplifier which drives, through a transformer, a recording head at the second tape. Specifications 786.033 and 786,036 also are referred to.