Patent GB-749207-A (GB)
Title: Improvements in or relating to magnetic storage computers
IPC: G11B5/02
Filed: 1953-09-15
Abstract: 749,207. Digital electric calculating-apparatus. WESTERN ELECTRIC CO., Inc. Sept. 15, 1953 [Sept. 18, 1952], No. 25453/53. Class 106 (1). Computing apparatus comprises a magnetic head associated with a magnetizable medium, sensing means and recording means each including the head, and means controlled by the sensing means and controlling the recording means for selectively changing the magnetization of areas on the medium. Two embodiments are described, viz. an adding and subtracting apparatus and a counting or " add one " apparatus, and each comprises a rotating magnetic drum from which are obtained both the number or numbers to be operated on (in binary series-mode form) and timing control pulses, the result of a calculation being rerecorded on the drum, and associated electronic circuits including varistor gates and the following basic elements of which detailed circuits are given (Figs. 9-14A, not shown): read amplifiers and read/write circuits such as AMP1 and RW1, Fig. 8, bi-stable double-triode trigger circuits such as KT, Fig. 7, and like trigger circuits such as RS having a single stable state, called " monopulsers " (MNP) and " pulse stretchers (PS), which are used for pulseshaping and lengthening. Adding and subtracting apparatus.-The magnetic drum DR, Fig. 8, has control tracks M, T which provide one pulse for every drum revolution and for every binary digit space or " cell " respectively, and tracks A, B on which the numbers to be added or subtracted are recorded A single head HM, HT, HA, HB is associated with each track, HA, HB being used for both reading and writing under control of associated read/write circuits RW1, RW2. The digit pulses obtained from HT are amplified in AMP2 and applied over line AO2 to pulse-shaping circuit RS, Fig. 7, to produce positive square read-synchronizing pulses, Fig. 15E, on line RS 1. These pulses are differentiated and their trailing edge triggers a similar circuit WS to produce write-synchronizing pulses, Fig. 15F, on WS1. The staggering of these read and write pulses enables a digit to be read from the drum and to be written over during the same digit or " cell " interval. The " mark " pulses from HM are similarly amplified by AMP1 and applied over line AO1 to circuit MM to produce positive square pulses, Fig. 15B, on line MM1. A multi-bank switch SW, Fig. 7, may be set to one of six positions to enable the following operations, described separately below, to be performed; (1) writing, (2) addition, (3) subtraction, (4) reading. (1) Writing.-A binary number set up on keys K1-Kn (selectively depressed to represent 1 or " X "), Fig. 6, may be written on drum track A or B, Fig. 8, by setting SW, Fig. 7, to position 1 or 2 respectively and depressing key AK thus applying a negative pulse, Fig. 15A, over line AK1 to trigger circuit KT. The trigger then applies a reduced potential, Fig. 15C, over line KT1 to the left-hand grid of double-triode gate G1. The next "mark" pulse on MM1 will cause momentary conduction in the normally cut-off right half of G1 thus applying a negative triggering pulse from its anode to circuit SU to increase the potential on line SU1 (see Fig. 15 B and D), and will restore trigger KT to normal thus re-closing the gate. The potential on SU1 will open gate SG, Fig. 6, comprising varistors V1, V2, so that pulses on SS1, Fig. 15 G, obtained by applying the " write " pulses, Fig. 15 F, to circuit SS, pass to line SG1 and are applied in differentiated form to the right-hand grids of double-triode trigger circuits ST, S1 to Sn and SE forming a stepping chain. The left half of each such trigger, except ST, is initially conducting, so that the trailing edge of the first pulse on SG1 will switch over ST only, Fig. 15 H, the resultant negative pulse at the left-hand anode being applied through capacitor 622 to switch over trigger S1, Fig. 15 I; the next pulse on SG1 will similarly restore S1 and switch over S2 (see Fig. 15 I and J) and so on up to Sn and SE, Fig. 15 K and L. Thus negative pulses will be obtained successively from the right-hand anodes of S1 to Sn connected to the keys K1 to Kn and are passed through varistors VO1 to VOn or VX1 to VXn (according to the key positions) to the grids of triodes WO, WX, Fig. 7, respectively. The anodes of these triodes are connected through resistors VO, VX to line WS1, and through banks of switch SW to lines TO1, TX1 and TO2, TX2 leading to the write inputs of circuits RW1, RW2 respectively, Fig. 8; thus, if e.g. SW is set in position 1, each positive " write " pulse, Fig. 18 F, on WS1 will be passed to line TO1 or TX1, according to whether the digit set up on the associated key is 0 or 1, to cause this digit to be recorded in track A. The pulse from the last trigger SE of the chain, Fig. 6, is passed to varistor VOE so that an 0 is recorded in the (n + 1)th digit place; this pulse also triggers single-stablestate circuit SR which, when it restores, causes the triggering of similar circuit CR and the resetting of trigger SU (see Fig. 15 D, M and N). The resultant long positive pulse on CR1, applied through cathode follower CRS to the right grid of ST, causes heavy current to flow through the right half of this trigger and the associated cathode load resistor 608, thus applying a positive voltage to the right cathode of SE to restore this trigger, and thus the whole chain, to the initial condition. (2) Addition.-Numbers previously written in tracks A and B may be added and the sum recorded in track A, by setting switch SW, Fig. 7, to position 5 and operating key AK. The positive potential on SU1 produced in response to the next " mark " pulse is applied to varistors VOS, VXS in " write O " and " write X" coincidence gates, Fig. 8. If resistors VOC, VXC also receive a positive potential from tube T4, these gates operate to write in A the opposite of what is read. Reading of the tracks is controlled by the pulses on RS1 which are applied to amplifiers R1, R2 which, every time they detect an " 1 " or " X," supply a triggering pulse over RO1 or RO2 to a PS circuit PA or PB respectively of which the output lines PAX, PAO and PBX, PBO are always at complementary potentials. Thus if a " 1 " is read in track A, PAX, connected to varistor VOR, will be at a relatively positive potential and PAO at a relatively negative potential, and the write pulse on WS applied to VOW will be passed through the " write O " gate to line WOO which is connected through switch bank SW1 in position 5 to " write O " line TO1. If, however, a " O " is read from A, PAO, connected to VXR, will be at the higher potential and the write pulse will be gated through VXW in the " write X " gate to line WXO connected through SW2 to line TX1. The carry is stored in a trigger CT and controls the gating of the read pulses, applied to varistor VRS, to triode T3 and the triggering input of circuit PC similar to PA and PB and having output lines PCX, PCO. The " change-A " potential applied to the write gates from tube T4 is obtained from coincidence gate VBO2, VCX or VCO, VBX2, these gates being operative when a carry digit is unaccompanied by a " 1 " digit from B or vice versa. The state of the carry trigger is changed only when the A and B digits are both " 1 " or both " 0 ", the trigger being then triggered to the " 1 " (or " carry ") or " 0 " condition respectively by a pulse on WS 1 applied through varistor coincidence gate G3, G4. (3) Subtraction.-The number in track B may be subtracted from that in track A by setting SW to position 6 and operating key AK, the operations being similar to those for addition except that varistors VA1, VA2 of gates G3, G4, Fig. 8, are connected through lines 712, 711 and switch banks SW4, SW3, Fig. 7, to lines PAX, PAO respectively (instead of PAO, PAX), since the trigger CT must be actuated when the A and B digits are 1 and 0, or 0 and 1. If the number in B was larger than that in A so that the difference is in complementary form (indicated by a " 1 " in the (n + 1)th position), the true magnitude of the result may be obtained by depressing key COM with SW in either the 5 or the 6 position, and then adding " 1 " (by writing it into B and performing an addition). (4) Reading.-The number in track A or B may be set up on gas discharge indicator tubes D1 to Dn and DE (for the (n + 1)th position) by operating " extinguish display " key ED, Fig. 6, which resets associated triggers DT1 to DTn and DTE to the zero-indicating condition, setting switch SW to position 3 or 4, and operating key AK. The line PAX or PBX, Figs. 8 and 7, is then connected through switch bank SW7 and line 702 to gating varistors V1B to VnB and VEB, and the stepping chain, Fig. 6, is operated, as described in connection with the writing operation, and applies positive pulses successively from the left-hand anodes of triggers S1 to Sn and SE to varistors VIA to VnA and VEA in synchronism with the reading of the tracks on the drum. Thus every " 1 " digit on the track A or B being read will produce a positive pulse on line 702 which will be gated to the appropriate trigger DT1 ... DTn, DE to switch it to the " 1 " condition in. which it causes the associated indicator tube to discharge. Counting apparatus.-In this apparatus (Figs. 2 and 3, not shown), the magnetic drum has similar control tracks M, T and a single number track with its associated read/write circuit. Writing on the latter track is controlled by " write O ", " write X " gates, similar to those of Fig. 8, which, during a counting cycle, are rendered operative to write the opposite of what is read until a " O " is changed to a " 1 " or " X ". A switch (SW) may be set to three operative positions in which the apparatus respectively counts the actuations of a key (AK), counts continuously after actuation of this key, and counts continuously until stopped by the key. Alternatively, a source of external pulses may be counted. Specifications 684,079 and