Patent GB-817597-A (GB)
Title: Calculating means
IPC: G06F11/10
Filed: 1956-09-14
Abstract: 817,597. Digital electric calculating-apparatus. STANDARD TELEPHONES & CABLES Ltd. Sept. 14, 1956 [Sept. 17, 1955], No. 28144/56. Addition to 777,286. Class 106 (1). A digital function which can take any value from 0 to p-1 where p is a predetermined integer, is calculated by electrical apparatus comprising a pair of p-condition ring counters, by alternately stepping a first counter at one rate while the second counter is stepped at r times the rate, until the first counter reaches a predetermined condition (e.g. zero), and stepping the second counter while the first counter is stepped at s times the rate, until the second counter reaches a predetermined condition, at least r of the integers r, s being greater than one. In a first arrangement, the condition attained by the first counter as a consequence of the two stepping operations is defined by x i+1 # s(rx i  - y i ) mod. p, where x i , y i  are respectively the numbers of steps required to bring the first and second counters from their initial conditions to the predetermined conditions and x 1+ i,  is the number of steps required to bring the first counter from the condition finally attained to the predetermined condition. If the above relation is used n times, the final condition X n+1  of the first counter will correspond to the function : Taking x 1 = 0 and y 1  as corresponding to the digits ai of a number, the calculation can be used to obtain the function : The arrangement shown, in which r=2, s= 1 and p = 11, is generally similar to that described in the parent Specification and comprises 11- stage counting chains CT 1 , CT 2 , e.g. similar to the circuit described in Specification 663,574 [Group XXXIX], and a control circuit CSC (Figs. 2 and 4, not shown) comprising electromagnetic relays, bistable and monostable circuits and gates. The arrangement is used for checking the typing of account numbers from cheques, these numbers being so chosen that the function : Each account number is keyed with the typewriter carriage in a left-hand position (contacts lk closed) and if the check is satisfactory, when an O.K. key (not shown) is depressed to close contacts ok, a signal is obtained at Ok which causes the stored account number to be printed and the carriage to be displaced to a right-hand position (contacts rk closed) for the amount on the cheque to be typed. When contacts lk are closed, a reset cycle occurs in CSC, during which counters CT 1 , CT 2  are stepped by pulses from terminals P 10 , P 9 , thus wiping out the amounts set thereon since the ring connections are broken by relay contacts cr 4 , cr 5 , CT 1  being subsequently set to " 0 " through relay contacts cdr 2 . When the first digit of the account number is keyed, operating one of contacts k 11 ... k 21 , k 01 , the corresponding stage of CT 2  is set ; since CT 1  is already at " 0," CSC supplies pulses at the same rate to P 9 , P 10 , until CT 2  reaches " 0 " when a pulse at P 7  is passed through gate G 2  to control circuit reset input P 13 , the digit on CT 2  having then been transferred to CT 1 . For subsequent digits set up on CT 2 , firstly twice as many stepping pulses are supplied to P 9  as to P 10  until CT 1  reaches " 0 " when the next pulse at P 7  is passed through G 1  to control circuit input P 12  to switch over a bistable device (BS 3 , not shown) after which the counters are stepped at the same rate, as described above, until CT 2  reaches " 0 ". When the whole account number has been entered, CT 1  should register " 0 " thus allowing a signal from device BS 3  to pass via P 11 , through gate G 3  to the contacts ok. If the O.K. signal is not obtained when these contacts are closed, the printing and carriage displacement will not occur, and the operator can depress a cancel key which closes contacts ck to reset the counters and other circuits. If the O.K. signal is obtained and the carriage displaced, the opening of contacts lk and closing of rk prevent the checking circuits operating while the amount is keyed. A further depression of the O.K. key returns the carriage to the left-hand position for typing the next account number. In a second arrangement (Fig. 5, not shown), in which the maximum time required for the entry of each digit is reduced, the keyed digits are entered alternately in the two counters which are controlled by a further bistable device to have their functions reversed after each entry (r=s==2). In a modification to further reduce the maximum digit entry time, stepping of a counter is stopped also if it reaches an intermediate stage (e.g. 5 in CT 2 ) which is 6 stages removed from " 0," one (1=(2x6) mod. 11) additional stepping pulse being fed to the other counter in such circumstances.