Patent GB-442602-A (GB)
Title: Improvements in ciphering systems and apparatus particularly for use in telegraph signalling systems
IPC: H04L9/38
Filed: 1934-08-17
Abstract: 442,602. Type-printing telegraphy. CREED & CO., Ltd., and SALMON, R. D., Telegraph House, Croydon, Surrey. Aug. 17, 1934, No. 23796. [Class 40 (iii)] [See also Group XV] In a ciphering system for printing letters, punching tape, or transmitting signals, a typewheel or like shaft is positioned jointly by gearing controlled by a keyboard operated in clear and by similar gearing controlled by a combination-setting device which changes its combination each time a key is depressed. Ciphering - apparatus. Four annular discs 22 have circumferences equal to different prime multiples (such as 53, 57, 59 and 61 respectively) of a unit length and are moved on by an interiorly gearing pinion 70 through one unit length for each character. The peripheries of the discs are variously notched so that they set up various combinations by causing four feelers 21 to set four rockers 19. The rockers act in known manner through four cams 20, four pairs of arms 25, 27, four bars 24, four half-revolution cams 13, and four sector arms 38 to set four differential gears 47, whose effects are additive and jointly control the position of a gear-wheel 52A in the manner described in Specification 436,296. The type-wheel 55 which prints in cipher is positioned jointly by the gear-wheel 52A and by gearing from a sleeve bearing a second type-wheel 46, which prints in clear and is controlled by means of a keyboard through combination bars such as 1, cams such as 4, and a set of differential gears 60. These gears are so dimensioned that half a revolution of the first gear produces , #, or if possible <1>/16, and <1>/32 of a revolution respectively in the second, third, fourth, and fifth gears. The ciphering gears 48 are similarly dimensioned, and since the four ciphering-rings 22 yield a maximum displacement of 16 letter spaces, the type-wheel 55 cannot be displaced by the ciphering-apparatus through a complete revolution. Case shift. The type-wheel 46, which prints in clear, has two rows of type representing letters and numerals respectively. The letters J- and Z are omitted from the letter row and the combinations representing these letters indicate shifts to numerals and to letters respectively. When the type-wheel 46 stops in a position corresponding to J or Z, a cam 40 on the same shaft permits one or other of the feelers 8, 10, Fig. 1 (which are intermittently actuated by a further cam 6) to shift a bar 39 and so to bring into the operative position one or other of the printing-hammers 71, 72. In the cipher wheel 55, however, the letters J, Z are retained and in the deciphered message these letters are regarded as shift-indications. Word-spacing and group-spacing. The letter X is used to indicate a space between words, and is enciphered and transmitted in the ordinary way ; but on the wheel 46, which prints in clear, a blank occurs in place of this letter. For the purpose of dividing the enciphered message into five-letter groups, the tape-feed ratchet 75, Fig. 3, is fed through two steps after every fifth letter, the throw of the pawl 62 being controlled to this end by a stop 61 which is positioned by a cam 76. The lever 61 also effects locking of the keys during the additional spacing movement. Change-over from cipher to clear and vice versa. When the keyboard is operated for upper-case letters F and H, the apparatus is set for clear and for cipher respectively by way of the rod 37, and these letters are replaced by blanks in the upper case of type-wheel 46. When these letters are keyed in the lower case no change of code is produced, the bar 37 being held by a lever 11 operated conjointly with the case-shift device 71, 72 ; but when the bar 37 is free to move it is, on depression of the keys for F and H, shifted to left and right respectively by feelers and a cam 50 similar to the parts 8, 10, 40, except that the cam 50 has notches like 9 but corresponding to the letters F and H. When, therefore, upper-case F is operated, the bar 37 moves to the left. It thus acts through bell-crank 15 to attach hook 16 to and detach hook 17 from a lever 36 which moves once per letter and sets the four rods to their zero positions by releasing four cams 31 which co-operate with four pairs of levers 28, 29, so that type-wheel 55 now prints in clear. When upper-case H is operated, the bar 37 is shifted to the right and ciphering recommences. Telegraphic transmission in cipher. The shaft of wheel 55, which prints in cipher, carries cams 64 which act similarly to the cams 20 and set five rods 63 similarly to the rods 24. The rods 63 may control a tape-perforator or a transmitter in known manner, and may be restored to the spacing position by lever 61, Fig. 3, for the purpose of signalling a space after every five letters. Deciphering - apparatus. This is similar to the ciphering-apparatus except that the drive from wheel 52A has to be reversed and the aggregate displacement derived from this wheel and from the cipher signals must be applied to the in-clear sleeve 46A instead of to the type-wheel 55.