GB910648A - Improvements in or relating to auxiliary apparatus for teleprinters for the automatic ciphering of messages - Google Patents

Abstract

910,648. Telegraph ciphering apparatus. ANSTALT EUROPAISCHE HANDELSGESELLSCHAFT. Dec. 16, 1958 [Jan. 7, 1958], No. 40576/58. Class 40 (3). In a ciphering and deciphering apparatus means responsive to a predetermined signal change the connections in the apparatus from the ciphering condition to the deciphering condition. The ciphering unit is provided with a selectively operated by-pass connection, the by-pass being switched in automatically if said signal is received while the ciphering unit is operating. In one embodiment, Fig. 1, during transmission a teleprinter at A passes signals to relay ER. Mark and space potentials are thereby passed to five capacitors C via a distributer. Each capacitor C feeds a by-pass switch D which applies the potential on C either via a distributer to relay SR or through contacts l and v to the distributer and relay SR. Contacts l and v are controlled by a cipher tape scanner and by a mechanical key, respectively. Contact sr causes signals to be transmitted on line B, the signals being in cipher or in clear dependent on the position of switch D. The apparatus is set to its receiving state a predetermined time after the end of a transmission by means of relay NG. During reception switches U 1 and U 2 are reversed, teleprinter A printing the received signals, after deciphering if necessary. If while the apparatus is transmitting in cipher, a special and predetermined signal is received on line B it is detected by unit K which reverses contacts U 1 and U 2 , and also sets switch S to the by-pass state. This is of use where, for example, the transmitter and receiver cipher tapes lose synchronism, the receiver then indicating that it wishes to correspond with the transmitter in clear code by sending the special signal. The signal further causes a visible and audible alarm S to be operated, and also opens switch Q so that message signals from the teleprinter A are not fed to the apparatus. In conditions of strong interference in the transmission path it is desirable to prepare a tape record of the ciphered message so that it may be repeated several times. This reduces synchronization problems that would arise if the message were ciphered each time it was repeated. To obtain the ciphered tape switch LO is reversed, signals from the teleprinter at A then being ciphered and recorded on a tape perforator connected at A. Should signals arrive on line B during this operation relay UE is operated, this energizing alarm S. Fig. 2 illustrates a modification to part of the apparatus of Fig. 1. Here the message is fed in from a tape scanner E, which controls the potential fed to the cipher tape scanner L, rather than from a teleprinter at A as in Fig. 1. The mechanical key is at V.