Patent GB-541909-A (GB)
Title: Improvements in or relating to multiplying machines
IPC: G06F7/46
Filed: 1940-05-13
Abstract: 541,909. Calculating apparatus. NATIONAL CASH REGISTER CO., Ltd., and SAXBY, F. R. May 13, 1940, No. 8581. [Class 106 (i)] In an electrical machine for effecting multiplication having registers into which the factors are entered and accumulator means for receiving the computed product and so arranged that the registers operate automatically and in step to form in one register a convergent series obtained by dividing the multiplier by successive powers of two and in the other register a divergent series obtained by multiplying the multiplicand by corresponding powers of two, ignoring fractional values in the resultant quotients, and provided with means which operate, when each odd value of the convergent series is formed, to enter into the accumulator the concurrently computed values of the divergent series to 'form a complete product, the said registers comprise groups of potentializable elements for each denomination of the original factors and for each possible denomination of any of the terms of the divergent series. In the machine shown for multiplying a quantity by a price, the multiplier register Fig. 1A comprises, for each denomination a set of digital value relays and a set of halving relays 0/5, 1/6, 2/7, 3/8 and 4/9, the multiplicand register Fig. 1, and Figs. 2, 3 and 5 (not shown) comprises sets of digital relays and doubling relays 0/1, 2/3, ... 10/11 for the units of pounds, pence, tens of shillings, and overflow denominations respectively. The circuit arrangement, Figs. 4 and 4A, with the registers connected as shown comprises also circuit control keys, sequence control relays BB, G, HJ and K for the halving and doubling operations a product entry control relay ZO, rotary selector switches KD, L, HM, N, P, Um and Tm, accumulator means such as telephone type meters MKD, ML, MH, MM, MN. MP, MA and MB, transfer relays COKD, COL, COH, COM, CON and COP and an interrupter INT for interrupting the feed to the rotary switches. In operation the main switch to the current supply is operated and then the start key is depressed. The energization of relay S renders the a and B lines alive and through a relay e and lines e and A energizes the left hand windings of the zero relays in the multiplicand register. The multiplier and multiplicand are then set up on the keyboards and the corresponding digital relays are locked. In the multiplicand register the right hand winding of the zero relays is energized to effect their release. The double windings are necessary to enable carry overs to be entered during the doubling operations into a denomination m which no digital relay has been operated by manual entry. An operation key OP is then depressed to control the sequence relays BB to K. If the lowest denomination of the multiplier is even the sequence relays cause the digital relays to energize their appropriate half transfer relays which pass back one half the value to the digital relays. These relays are subsequently de-energized if the half value is even without first being locked. At the same time in the multiplicand register the transfer relays pass back double the value of the multiplicand. BB relay, which has de-energized is again energized through the relay G and concurrent halving and doubling operations take place. If, however, the entered multiplier, or a derived half value, is odd, then the product entry control relay ZO is operated to short circuit relay BB and close a circuit to the driving magnets of the rotary switches through the interrupter INT. The finder switch arms step up find the lines marked by the operation of the digital relays and the meter wheels stepping up in unison accumulate the product. When all finder switch arms have found live contacts a chain of contacts KD 2  ... P, will have been closed to energize a normalizing relay E to short circuit the product entry relay ZO thus re-energizing the relay BB to initiate another halving and doubling operation. The normalizing relay E is also dependent for its operation upon the carry over relays COKD to COP and relays Y and T so that all necessary transfers are completed before the next operation of the sequence relays. After the value O1 has been reached in the multiplier register a final cycle is performed to obtain the value OO; the product entry relay ZO does not operate but a relay R is energized to de-energize all the digital relays. Metal rectifier elements have been inserted in the rotary switch and relay R circuits to prevent feed back. Re-setting the meter wheels to zero is effected on depression of a zeroizing key which energizes a solenoid SO to displace a detent bar and operate the interrupter INT to step the wheels to zero position and release the operation key. The multiplier entered on the keyboard may be read on the meter wheels MA, MB, on the operation of a read key with contacts RE 1 , RE 2  and RE 3  which energizes the interrupter INT to operate the rotary switches Um, Tm. By means of a similar arrangement (not shown) the factor entered into the multiplicand register may be set up on indicator wheels prior to a multiplying operation.