Patent GB-577940-A (GB)
Title: Improvements in or relating to electrically operated calculating apparatus
IPC: G06F7/40
Filed: 1941-07-21
Abstract: 577,940. Calculating - apparatus. STANDARD TELEPHONES & CABLES, Ltd., HARTLEY, G. C., HAIGH, L. B., and GOULD, J. R. July 21, 1941, No. 9193. [Class 106 (i)] An electrically-operated calculating-apparatus comprises means for entering thereinto a number expressed in radix two, electrical means for computing the equivalent in radix ten, and means for rendering the computed number available. In the form shown in Fig. 1, for indicating a radix ten number having not more than two digits, the circuit arrangement is such that the number entered can be expressed as the sum of a series of lesser magnitudes. The circuit includes means for performing an attempted series of subtractions of the numbers expressing said lesser magnitudes in decreasing order, e.g. 80, 40, 20 and 10. The radix two number is entered by applying ground to such of the wires a<3> ... g<3> as correspond with the digital value 1 in the number. Simultaneously, ground is applied to the start wire ST to operate a relay DA and thereby appropriate relays IA ... IG and relay XX. Relays IA ... IG lock over their front contacts and apply ground to the wires a ... g in a device represented by the rectangle S which includes a subtracting circuit arrangement as described in Specification 577,893. 'The first subtract operation is attempted by applying ground to the wires a<1>, c<1> in accordance with the first lesser magnitude (80) and the remainder appears on the wires b<2> ... g<2>. These wires are connected by the contacts of relay XX to the relays RB ... RG to store the remainder temporarily. If the subtraction is possible, the remainder will be positive and relay X will operate through closure of contact p and will operate relay SA which locks. Relay XX is released and the locking circuits of relays IA ... IG are opened. Relay DB then operates and releases relay DA. Relay X is released, after delay, to allow relays IB ... IG to re-operate in accordance with the conditions of relays RB ... RG to receive the remainder which is then entered as the new minuend on the wires b ... g in the circuit S. If subtraction was not possible, the relay Z operates through contact n to break the circuit to relay XX and to cause operation of relay DB so that the number originally entered remains in the circuit S. The second subtraction is then attempted by applying ground to the wires b<1>, d<1>, in accordance with the next lesser magnitude (40). Relay X or relay Z will be operated according as a subtraction is, or is not, possible. If subtraction is possible, relay SB is operated and the remainder is locked in the relays RB . . . RG. If subtraction is not possible, relay SB is not operated and the original number or the previous remainder remains stored in the relays IA . . . IG. A similar sequence of operations takes place, when the relays DC, DD are operated, over the wires c<1>, e<1> and d<1>, f<1>, in attempt to subtract and-operate relays SC, SD. After the last release of relay XX, relay DE operates to complete the circuit to indicator lamps I, the operation of the relays SA, SB, SC or SD will determine the tens digit, while the remainder on relays RB . . . RG will determine the units digit. The same process may be extended to the conversion of decimal values. In another form, Figs. 2 and 3 (not shown), the radix two number is entered digit by digit by a pair of keys 1 and 0, or by multiposition switches or other contact arrangement. The circuit comprises a set of sequence relays and a set of computing and aggregating relays which operate by a process of repeated doubling and adding. In another form, Figs. 4 to 6 (not shown), the digits of the radix two number are entered simultaneously and each digit is transformed into an equivalent number in radix ten and the final number computed from the sum of said equivalent numbers. Specifications 577,895 and 578,041 also are referred to.