GB1508971A - Teleprinter systems - Google Patents

Abstract

1508971 Data transmission; ciphering SIEMENS AG 27 Aug 1963 [27 Aug 1962] 33825/63 Heading H4P In a system for enciphering, transmitting and deciphering teleprinter signals which are transmitted from a transmitting station to a receiving station, (i) a series of unciphered teleprinter characters are enciphered by mixing with a series of message cipher characters produced from a message cipher generator at the transmitting station, the enciphered characters so formed being transmitted to the receiving station, (ii) separate synchronizing means provided at the transmitting station and the receiving station operate continuously, during both message transmission and pauses in message transmission, (iii) a message cipher generator at the receiving station is operated in synchronism with the message cipher generator at the transmitting station to produce an identical series of message cipher characters, (iv) the series of enciphered message characters received at the receiving station is mixed with the series of message cipher characters produced at the receiving station to produce the original series of unciphered characters, and (v) means are provided at the transmitting station to continuously transmit cipher signals during pauses in message transmission. Preferably, during pauses in message transmission a pause cipher distinct from the message cipher is transmitted from the transmitting station to the receiving station. At the transmitting station "message start" and "message end" signals cause the pause cipher to be switched in and vice versa, respectively: The "message start" and "message end" signals are mixed with the message cipher before transmission, and after mixing with the message cipher at the receiving station the resulting unciphered "message start" signal is employed to effect recording or read-out of the following signals and the resulting unciphered "message end" signal is employed to terminate read-out or recording of the received signals. The start and stop elements of start-stop teleprinter characters are employed to check synchronism between the transmitting and receiving stations. The transmission of a special service code results in the direct connection of a service teleprinter to the transmission line at the receiving station.