Patent GB-1506741-A (GB)
Title: Apparatus for mixing plain language characters with ciphering characters
IPC: H04L9/18
Filed: 1961-03-20
Abstract: 1506741 Data transmission; ciphering R HELL 20 March 1961 [21 March 1960] 10152/61 Heading H4P  Apparatus for mixing plain language characters with ciphering characters, particularly teleprinter characters, comprises a plain language or secret character transmitter (represented by a decoder 7 in the embodiment described) synchronized with a ciphering character transmitter (represented by a decoder 21), an enciphering or deciphering output device 27, permutation switches 8,9, 10 ... equal in number to the number of characters (e.g. 26 or 32) in the alphabet used and each having a similar number of inputs and outputs, and AND-gates 12, 13, 14..., 23, 24, 25... connected one to each output, the first control inputs of the AND-gates allocated to each permutation switch being connected to an output each of the corresponding permutation switch, the second control inputs of the AND-gates allocated to each permutation switch being connected to an output each of the decoder 21, and the parallel-connected outputs of corresponding AND-gates (i.e. of equal ordinal numbers) of all the permutation switches being connected each with one input of the device 27. When the teleprinter 1 is operated, pulses pass through a gate 3 and conductor 4 to a pulse storer 5 and when a complete character has been received, pulses are passed as a potential configuration through the conductors 6 to the decoder 7 and one of its output terminals becomes live, e.g. terminal (17). This terminal is connected to each of the terminals (17) of the permutation switches 8, 9, 10... which, in the embodiment described, are mechanical rotary switches operated by means of a common rotary shaft. These permutation switches are different from each other and are made as plugin units so as to be exchangeable at intervals. Current flows from the corresponding output terminals to the first control inputs of AND-gates 12, 13, 14... but before any one of these gates is opened, current must also flow to its second control input. This is effected as follows: decoder 7 is synchronized through a differentiating circuit means 17 to a punched strip scanner 15 which scans a ciphering punched strip 19, the hole combinations of which are fed as potential configurations through the five connecting wires 20 to the decoder 21, one of the output terminals, e.g. terminal (16) of which becomes live and passes current to each of the AND-gates 13, 23, 24, 25... allocated to permutation switch 9. Only AND-gate 13 is prepared for opening, however, and current passes through this gate and conductor 26 to input terminal (7) of device 27 and the corresponding character is transmitted as a potential configuration through conductors 28 to pulse storer 29 and then as successive pulses through conductor 30 and gate 31 to the far distance line 32. The next character from the teleprinter 1 is enciphered in a similar manner, the permutation switch used depending on the next hole-combination of the punched strip 19. When the apparatus is used for deciphering, the pulses received by pulse storer 33 through gate 34 and conductor 35 are fed through conductors 36 to the input terminals of decoder 7 and the above process repeated but with the permutation switches 8, 9, 10... rotated through 180 degrees. Where the permutation switches are symmetrical about their longitudinal axes, this rotation is not required. Instead of mechanical permutation switches, a quadratic ring core storage matrix with thirty-two ring core columns with thirty-two ring cores each may be used. In the deciphering process, the teleprinter characters must then be trial-enciphered in turn until a secret character obtained in this way agrees with the secret character to be deciphered. The teleprinter character just being enciphered is then the plain language character required.