Teleprinter secrecy system

Abstract

Abstract 865,938. Type printing telegraphy. ATELIERS DE CONSTRUCTION ELECTRIQUES DE CHARLEROI. Feb. 19, 1959 [Feb. 14, 1958], No. 3763/59. Class 40(3) A system of the type described in Specification 766,200, which comprises means for converting five unit code signals to a signal formed of two frequencies chosen from twelve, is modified in that the correspondence table is varied according to an arbitrary code which ciphers the five unit code signal by inversion of some or all of its code elements. Deciphering means is provided at the receiver. In operation, each clear five unit signal is converted according to the correspondence table, to two signals which are fed via two of twelve input terminals 1-12, Fig. 4, through relay contacts to two of twelve oscillators connected at 1<SP>1</SP>-12<SP>1</SP>. The relays 13-17 associated with the relay contacts are actuated by the presence or otherwise of perforations in a cipher tape containing five tracks. Thus if there is no perforation contact 18 does not close and an input on terminal 8 will pass to terminal 8<SP>1</SP> and cause an oscillator to operate. However, if relay 13 is operated due to contact 18 closing through a perforation, an input at 8 passes to 4<SP>1</SP> causing a different oscillator to operate. If relay 14 also is operated the output appears at 6<SP>1</SP>. The five unit signal is thus ciphered. At the receiver incoming signals are converted to five unit signals according to the correspondence table and fed to discharge tubes 57-61, Fig. 5. On reception of a signal on tube 57, relay 47 reverses contact 42 which operates the selector magnet 52. However if the cipher tape at the receiver indicates that that code element had been inverted at the transmitter, i.e. if contact 32 is closed, relay 27 reverses contacts 37 and the magnet 52 is then not energized. The received signal is thus deciphered. Alternatively the selector magnets 52-56 may each have two windings operating in opposition and fed one with the ciphered five unit element derived from the received signals and the other with a signal corresponding to a perforation in the cipher tape.

Inventors

• 👤 Jean Jacques Cuvelier

Bibliographic Details