Patent GB-577195-A (GB)
Title: Improvements in or relating to calculating machines
IPC: G06F7/46
Filed: 1944-03-29
Abstract: 577,195. Calculating - apparatus. BRITISH TABULATING MACHINE CO., Ltd. March 29, 1944, No. 5841. Convention date, March 30, 1943. [Class 106 (i)] An electrically-operated machine comprises means for performing multiplication by the direct method, means for performing division automatically bv multiplying the divisor by each of a plurality of different amounts and comparing each product obtained with the dividend to obtain the quotient, and means for extracting the square root of a number. According to the invention for multiplication, the entry of the multiplicand digit selectively energizes a set of four relays in accordance with the first four terms of the binary system to close related contacts and complete circuit connections through contacts set by the multiplier digit and arranged according to the same four terms so as to energize sub-product relays, representing the product of each binary value of the digit of one factor by each binary value of the digit of the second factor, and thereby to complete a results circuit to indicate the final product. In obtaining the result 87 x 95=8265, Fig. 3 shows the factors expressed in the binary equivalent and the various sub-product relays and carry relays C that are energized to give the final product. In the machine described for two digit factors, numeral keyboard 10, 11, Figs. 1c, 1d, are provided for setting the multiplier and multiplicand. The value keys on depression are held by latch bars 12 and close contacts 13, 14, in accordance with the binary coding 1, 2, 4 and 8. The contacts 14 in each denomination are arranged in circuit with leads 20, normally closed contacts of a relay R1, and the leads 21 of four corresponding relays 19 with two opposed windings as shown in Figs. 1a, 1b. Each relay 19 is provided with sets of contacts 23, 24 and 25 arranged in circuits with the contacts 13 of the multiplier keys and with the leads 28 of the multi-contact product relays R1.1 to R8.8 shown in Figs. 1g, 1k for the units denomination. To initiate this' operation current is supplied to leads 15, 16 and a multiplication control key 17, Fig. 1e, is depressed to shift contacts 18 to complete the results circuits associated with the factors set. Transfer of values from the units denomination to the tens is under control of the carry relays C1-C6 with contacts arranged in the tens summation leads. The final product is indicated on lamps 41, Figs. 1c, 1d and 1e. The circuits are opened on depression of the zero keys 10 and 11 or on the setting of a new pair of factors. Division operation. For this computation the dividend is set up on the keys 11, Figs. 1c, 1d and 1e, and if necessary on keys 11, Fig 1f (not shown), and the divisor is set up on the keys 10, Figs. 1c and 1d. A division control key 50 is then depressed to close contacts 51 to energize relay R1 and the operation is initiated by momentarily depressing a start control key 56. The-process involves the use of the multiplying circuits to set the relays 19 to represent successively different multiples of the divisor and to compare these amounts with the dividend. When the trial product is less than the dividend, the corresponding relay 19 is held energized. The comparing mechanism includes the stepping switch, Figs. 1a, 1b, relays R50, R51, contacts 74 and contact blades 72 operated on depression of the dividend keys to close contacts 73 and all those to the left. The stepping switch controls the sequence of operation and includes wipers 54, 60, 62 and 63 arranged on a shaft actuated by a ratchet and pawl 61 under the control of a relay S, the energization of which is effected by a slow-acting relay SL when the key 56 closes its contacts 57 and the wiper 60 is in the normal position as shown. The stepping of the switch continues automatically under control of the wiper 60. When the wiper 61 contacts the " 1 " segment, a relay R11 operates to break any holding circuit of the relays and then recloses its contacts R11a. The wiper 62 energizes, in turn, the lower winding of the relays 19 and shifts their contacts 23, 24 and 25. When the " 2 " segment is contacted, the " 8 " relay 19 of the tens denomination is energized and a multiplication takes place to obtain the product of the divisor x 80 which is displayed on the lamps. The comparing circuits ascertain whether this trial product is greater or less than the dividend. If the product is less, the relay 19 remains energized, if greater the circuit through the wiper 63 and relay R50 is completed to de-energize the relay 19. The other relays are acted upon in sequence. On return of the stepping switch to initial position, the wiper 60 disconnects the relay SL to interrupt the switch. At this moment the relays 19 are energized in a condition to represent the quotient and the wiper 54 is in its normal position to complete a circuit to a relay R9 to shift its contacts so as to complete a circuit through the upper contacts R9b, the " 1 " contact R10a of relay R10 and the " 1 " wire 27. The lower contacts R9b and the contacts R10a being disconnected, a result multiplying circuit is energized to obtain the product of the quotient by " 1 which is displayed on the lamps 41. Extracting square root. In this operation, the relays 19 are successively energized in the same manner as for division ; the number whose root is sought is set up on the keys 11 and nothing is set on the keys 10. Upon depression of the square root key 82 and the closure of the start contacts 57, relays R1 and R10 are energized to disconnect the key contacts 13, 14 from the multiplying relay selection circuits. Shifting of the relay contacts R10a connects the wires 27 with a group of wires 70 and the contacts 24 of the relays 19. This causes each trial value set on the relays 19 to be multiplied by itself and compared with the number set on the keys 11. When the resulting comparison indicates a condition of equality in all orders, the setting is multiplied by 1, whereupon the wipers return to home position and operate the lamps 41 to represent the square root.