Patent GB-593464-A (GB)
Title: Improvements in or relating to multiplying machines
IPC: G06F7/52
Filed: 1944-05-19
Abstract: 593,464. Calculating apparatus. NATIONAL CASH REGISTER CO. May 19, 1944, No. 9744. Convention date, March 21. 1942. [Class 106 (i)] A multiplying machine operating on the binary system comprises a product totalizer formed from denominational pairs 'of electricdischarge tubes, multiplicand and multiplier units each containing a discharge tube for each multiplicand and multiplier denomination respectively, and a partial-product unit having a number of discharge tubes equal to the product of the numbers of denominational tubes in the multiplicand and multiplier units. In the embodiment described, the highest multiplier tube operates to prime a corresponding group of partial-product tubes if a multiplier digit is entered in the denomination in question. The multiplicand tubes then operate in sequence. As each multiplicand tube operates, it causes operation of that one of the primed partial-product tubes corresponding to the multiplier digit X the said multiplicand digit, the resulting impulse passing to the totalizer. When all the multiplicand tubes have operated, the next multiplier tube operates to prime another group of partial-product tubes, all the multiplicand tubes again functioning in sequence; this is repeated for each multiplier digit. Product totalizer ; zeroizing and transfer arrangement. This comprises a pair of gasfilled electric-discharge tubes 10, 11, Fig. 1. for each denomination, so interconnected that, if one tube be conducting the other is extinguished and vice versa. " 0 " is registered when the right-hand tube 11 is conducting, " 1 " when the left-hand tube 10 is conducting. The totalizer is zeroized by a key 27 which earths the control grids of all the right-hand tubes, thus causing all these tubes to fire, i.e., become conducting. A'positive impulse arriving at the lowest (2‹) denomination input terminal 29 raises. the potential of the control grid of the tube 10 and causes this tube to fire. The initial anode current (the anode being in effect at the start of firing temporarily earthed through condenser 18 and relatively low resistance 19) causes a drop across a resistance 17 in the anode supply circuit sufficient to extinguish the tube 11. The normal cathode current passes through a relatively high resistance 12. The next impulse arriving at the terminal 29 extinguishes the tube 10 and fires the tube 11, the resulting potential rise in the cathode circuit of tube 11 forming a transfer signal which is transmitted via a line 32 to the control grids of the tubes 37, 38 forming the next higher denomination. Partial-product unit. The result of multiplying any digit of the multiplier by any digit of the multiplicand is, in the binary system, either " 1 " or " 0." The network comprises, in the case where each factor may have up to three digits, nine gas-filled electric discharge tubes, Fig. 2. If the third (2<2>) denomination of the multiplier contains the digit 1, potential is applied to a terminal 50 from the multiplier unit, described below. This releases the negative bias on the grids of the first row of tubes 51, 52, 53, but not sufficiently to cause these tubes to fire. If the third (2<2>) multiplicand denomination contains the digit 1, potential is now supplied to a terminal 60 and this fires the prepared tube 53, whereby an impulse is transmitted to the terminal 41 connected to the 2<4> denomination of the totalizer. Multiplicand impulses are supplied in succession to terminals 60, 61, 62 in those cases where the corresponding multiplicand denominations contain the digit " 1." Thus, if such a digit is present in the lowest (2‹) multiplicand denomination, terminal 62 is energized and prepared, tube 51 fires to send an impulse via a line 56, 55 and terminal 39 to the 2<2> denomination of the totalizer. Potential is now removed from the terminal 50 and, if the second (2<1>) denomination of the multiplier contains the digit 1, the terminal 82 is energized, by means described below, to prepare the second row of tubes 64, 68, 71 by relieving the negative grid bias. Potential is next again applied in sequence to those terminals 60, 61, 62 corresponding to multiplicand denominations containing 1. This causes the corresponding ones of the prepared tubes 64, 68, 71 to fire and cathode impulses to pass to the appropriate denominations of the totalizer. Thus, a potential impulse given to terminal 61 (2<1>) will now fire tube 68 to send an impulse via the line 55 to the terminal 39 of the 2<2> denomination in the totalizer. The whole process is finally repeated with the 2‹ multiplier terminal 83 energized, if the lowest multiplier denomination contains 1. Multiplier unit. This comprises a gas-filled electric-discharge tube 100 ... 102, Fig. 3, for each multiplier denomination, together with a stop tube 103. The multiplier is set by closing digit-key switches 84 and a switch 104 is then closed. This earths the grid of the highest tube 100, which fires, whereupon, if switch 84 is closed, relieving potential is supplied to the terminal 50. This potential is also sent to the grid of the second tube 101 to prepare this for firing. An impulse is now received at a terminal 105 from the multiplicand unit, described below. This fires the prepared tube 101, the initial anode current through line 109 causing a potential drop across a resistance 108 sufficient to extinguish the tube 100. The rise in cathode potential at the point 152 prepares the tube 102 and, if switch 2<1> is closed, the rise is also transmitted as the relieving potential to terminal 82, Fig. 2. The next impulse at terminal 105 fires tube 102 and the next the stop tube 103. The anode current for this tube, passing through a resistance 128, causes a potential drop on a terminal to stop the operation of the multiplicand unit. In a modification, not illustrated, multiplier tubes corresponding to denominations in which no multiplier digit is set are byepassed by key switches. Multiplicand unit. This has a respective gas-filled electric-discharge tube 203, 202, 201, Fig. 4, for each multiplicand denomination, together with a control tube 200. Digit-key switches 256, 276, 277 are depressed in those denominations in which the multiplicand contains 1 and a start key 223 is also depressed. This applies positive potential from a line 206 to the grid of the highest tube 203, the tube thereupon firing, the resulting potential rise in its cathode circuit being conveyed to the grid of a relay tube 241. If the digit key 277 is in depressed condition; the normal grid bias of relay tube 241 is relieved and the tube thus fires with the tube 203. The potential rise of the relay tube cathode is conveyed to the terminal 60, Fig. 2, of the partial-product network. The potential rise in the cathode circuit of tube 203 acts on the grid of tube 202, causing this tube to fire. The resulting voltage drop in the anode circuit, caused by a resistance 208, extinguishes the tube 203. If its grid has been prepared by closing the digit key 276, a relay tube 240 then fires to give a potential impulse to the partial-product network via terminal 61. The firing of tube 202 also automatically fires tube 201 and this extinguishes tube 202. Control tube 200 is then fired and this in turn fires the highest tube 203 once again and also send a control impulse to the multiplier connection 105. The cycle is repeated for each multiplier denomination, until finally the stop tube 103, Fig. 3, is fired and this, by reducing the potential of point 126, prevents the firing of tube 203 to start another cycle. In a modification, not illustrated, multiplicand tubes corresponding to denominations in which the digit is set are byepassed by key switches. Relays 239 ... 241 may then be dispensed with.