Patent GB-848542-A (GB)
Title: Improvements in or relating to devices for determining check symbols for symbol groups and/or for checking symbol groups already provided with check symbols
Inventor: REUMERMAN THEODORUS
IPC: G06F11/10
Filed: 1956-04-11
Abstract: 848,542. Digital electric calculating-apparatus. REUMERMAN, T., and HELMIG, W. H. T. April 10, 1957 [April 11, 1956], No. 11050/56. Class 106 (1). In a device for determining check symbols for symbol groups and/or for checking symbol groups already provided with check symbols, numerical symbol groups are checked on the basis of a value N, e.g. 11, 13 or 17, and alphabetic and alpha-numerical symbol groups are checked also on the basis of a small prime number M e.g. 5 or 7. As described, alphabetic and alpha-numerical symbol groups have two check symbols based on N = 13 and M = 7 respectively. The checking device shown is applied to a punching machine in which numerical digits 0-9 are each entered by actuating the corresponding key and letters by actuating one of the " overpunch " keys O, X, Y in combination with one of keys 1-9, auxiliary symbols being entered by keys X and Y actuated alone. The keys actuate contact banks B1, B2 to mark one of 38 output lines L2 each connected through corresponding rectifiers G1, G2 to an input of 13-computer C1 and 7- computer C2. For checking purposes, each digit has assigned to it a value such that R 13  (the remainder when divided by 13) gives the value of the digit and R 7  is zero (e.g. the value 28 is assigned to digit 2); and the letters are divided into a first group of 13 given values 7a + b (a = 0, 1 ... 12 and b = a constant), a second group of 7 given values 13c + d (c = 0, 1 ... 6, d = a constant), and a third group, also including the auxiliary symbols, for which the values may be arbitrarily chosen provided they are less than 91 and have not already been used. The letters in the first and second groups are used for the first and second check symbols respectively and, in the example given, b = 2 and d = 10. The computers C1, C2, due to the rectifier connections, effectively receives quantities equal to the remainders R 13 , R 7  respectively for the values assigned to the entered symbols, and are arranged to produce the remainders R 13 , R 7  of the numbers formed from these entered quantities it can be shown that if a symbol group followed by its two check symbols is entered correctly computers C1, C2 should be in their check positions in which they register " 9 " and " 2 " respectively. If the check is satisfied, device CD allows punching to be performed and resets the computers to zero through line L3. When the device is used for determining check symbols the outputs of computers C1, C2 may be connected to indicating glow lamps. A letter relay LR controlled by contact banks B1, B2 inhibits the output of C2 until a letter has been entered. In a modification in which the zero positions of the computers are the check positions, the second group comprises 6 letters only which are given values 13c (c = 1, 2 ... 6) since the value " 0 " is reserved for digit 0; for that value of R, for which the missing value of the second group would be required the order of the check symbols is reversed. Another embodiment described and shown in detail, in which the computer check positions are 3 and 2 respectively, comprises relay contact networks whose operation is controlled by timing relays.