Patent GB-591680-A (GB)
Title: Improvements in or relating to electrically operated calculating equipment
IPC: G06F7/40
Filed: 1945-05-02
Abstract: 591,680. Electrical calculating- apparatus. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd., and BAKER, G. T. May 2, 1945, No. 11051. [Class 106 (i)] Electrical calculating apparatus comprises a rotary stepping switch in which the wipers of the switch are adapted to transfer the setting of a group of storage relays to a group of common relays which thereupon control the setting of the storage relays to a different value. Embodiments are described for addition and subtraction on the binary scale, multiplication and division on the binary scale and addition on the denary scale. Fig. 1 shows a storage relay of the type used in all the embodiments. Connection of lead A to battery energizes relay UR which locks up over contacts UR1 until the lead A is earthed when the relay releases. Relays of this type, representing numbers on the binary system, are connected to successive contacts of banks S1, S2 of a rotary stepping switch, Fig. 2, the relays S1 acting as a counter and the relays S2 as entry storage means. Energization of a magnet P energizes magnet SM which releases magnet P to advance the uniselector one step. In each order, when the effective contacts of banks S1, S2 are connected to operated storage relays, relays A, B energize over their upper windings and if there is a carry from a lower order, relay C is also energized. When relay P operates, wipers S1, S2 are disconnected from relays A, B, Wiper S2 is earthed to shunt down its associated storage relay, and depending on the sum, wiper S1 is connected or disconnected to battery or earth to energize or de-energize its relay or leave it in its existing state. In the case of carry to the next order, relay D operates and prepares a circuit for relay C when relay P releases to step on the uniselector. Subtraction. Reversal of contacts SUB prepares the circuit for subtraction. With a larger capacity than is required, a negative answer is indicated by the operation of the highest relay. Multiplication. Two two-bank uniselectors SA, SB are used, the multiplier and multiplicand being entered on banks SA2, SB1 and the product being obtained on SA1. The process involves a cycle for each operated relay in the bank SA2, the number in the bank SB1 being added into the bank SA1 with appropriate binary denominational shift. The magnet SAM is operated at each operation of magnet P, but the magnet SBM is operated after the first step only when relay SW operates, i.e. only when a significant digit occurs in bank SA2, whereby the appropriate lead is given to uniselector SA. When the uniselectors reach an operative contact in bank SA2, relay SW operates to operate magnet P, magnets SAM, SBM energize to release relay P and the two uniselectors step together. Contacts P2 connect earth to SA2 to shunt down the operated storage relay in that bank, while relay ON energizes to disconnect the wiper SA2 so that the remaining storage relays in that bank have no further control during the cycle. The number on bank SB is now added into bank SA1 in the same manner as in Fig. 2 except for the denominational shift. The process is repeated for each operative relay in bank SA2, the uniselector SA gaining one or more steps each cycle. Division. Division can be performed if the wiper SB starts several steps in front of the wiper SA, losing one step in the home position each cycle. When subtraction of the divider leaves a negative dividend, zero is entered in the appropriate order of the quotient and the divider is added in the next lower order. This produces a short division. Further apparatus (Figs. 4 and 5, not shown), is described for performing addition on the decimal scale, each denomination having four storage relays arranged on the binary system and connected to the contacts of a uniselector, each fifth contact of which is arranged to control carry-over from one denomination to the next. The circuit is based on that of Fig. 2.