Patent GB-577893-A (GB)
Title: Improvements in or relating to electrically operated calculating equipment
IPC: G06F7/40
Filed: 1941-04-24
Abstract: 577,893. Calculating apparatus. STANDARD TELEPHONES & CABLES, Ltd., HARTLEY, G. C., HAIGH, L. B., and - REYNOLDS, W. J. April 24, 1941, No. 5285. [Class 106 (i)] Electrically-operated calculating-apparatus for numbers expressed in radix two comprises means for entering first and second numbers and for representing each of said numbers by the condition of a separate set of two-position devices, and means automatically co-operating with the sets of devices to represent the algebraic sum of the said numbers by the condition of a third set of two-position devices. An apparatus for adding or subtracting two numbers expressed in radix two is shown in Fig. 4 and comprises two sets of relays BA . . . GA and BB . . . GB (not shown) for entering the numbers, associated contacts arranged in circuits similar to that shown in Fig. 2 and represented by the blocks CO, output wires connected to other contacts arranged in circuits similar to that shown in Fig. 1 and represented by blocks S, and relays AR ... GR in the output circuits to determine the result. In the lowest denomination, the contacts of relay GA corresponding to Al, Fig. 1; are omitted since there is no carry-over from a lower denomination. In the highest denomination, the condition of the relay AR is determined directly by the output from the carry-over circuit of the relays BA, BB. For subtraction operations, a relay (not shown) is operated to shift over the normal position of the contacts 'A3, A4, Fig. 2. 'The number representing the solution may be displayed by arranging the front contacts of the relays AR . . . GR in lamp circuits. As an alternative, two output wires may be provided for each denomination, the digital values 1 or 0 being represented by ground potential on one or other wire, the circuit being arranged as shown in Fig. 5 instead of Fig. 1. A circuit arrangement for successive addition and subtraction operations is shown in Fig. 6 adapted for numbers 2<o> up to 2<N> with a denomination 2<N+1> to provide for carry-over. Potential is applied, from an external control source, at the terminals IA or IA<1> when numbers are to be added, at the terminals IS when a number is to be subtracted, and at the terminals O when it is desired to obtain the solution. The circuit includes sets of digit entering, retaining and aggregate relays A, NA ... OA ; S, NS . . . OS ; Z, NZ ... OZ ; and B, NB ... OB with contacts arranged as described with reference to Figs. 1, 2 and 4, control relays ZP, AP, a calculating relay C, a timing relay T, a resetting relay E, and an alarm relay AL. A first number enterd at IA<1> sets the aggregate relays Z and retaining relays B. A second number entered at IA concurrently with or following the first number sets the relays A. These entries control the relays ZP, AP and C ; the relay C completes a circuit through the contact arrangement to enter the new aggregate in the relays Z and operates the timing relay T. This relay operates to release the relays A, breaks the circuit to the relays B and recloses in the circuit in accordance with the new aggregate over the contacts Z3, NZ3 . . . OZ3. When the relay T is released by the control relays, potential can be applied to the terminals 0 in accordance with the aggregate to exhibit the result. Subtraction is effected by adding the complement. Specification 571,687, [Group XXXVIII], is referred to.