Patent GB-832544-A (GB)
Title: Improvements in or relating to teleprinters and systems for enciphering and decipheriing teleprinter messages in multi-unit code
IPC: H04L9/18
Filed: 1957-03-21
Abstract: 832,544. Type-printing telegraphy. SIEMENS & HALSKE A.G. March 21, 1957 [March 21, 1956; Jan. 18, 1957], No. 9359/57. Class 40 (3). A teleprinter comprises a plain text contact and a cipher key contact controlled respectively according to the code elements of message signals and cipher signals and includes a single ciphering or deciphering relay so connected with the plain text contact and the cipher key contact that its armature assumes one position when the plain text contact and cipher key contact are both open or both closed and assumes another position when one of the said contacts is open and the other is closed. The plain text signals from the contacts HS or LS, Fig. 1, of a transmitter operated by a keyboard or perforated tape respectively and the ciphering signals from the contacts SS of a cipher transmitter are applied to windings (5, 8) (1, 4) of a relay MR having a biasing winding (9, 12) operating the relay so that its contact mr is in its upper or spaced position when the plain text contact LS or HS and the cipher contact SS are both open or both closed. The latter condition obtains during the step impulse of the message signal, and the winding (1, 4) of the relay SR energized, when contacts KV1 close, holds contact sr closed on the transmitting line L. When the message contact, HS or LS, and the cipher contact SS are in opposite conditions, a circuit is completed through winding (1, 4) or (5, 8) of the relay MR, which overpowers the biasing winding (9, 12) and its contact mr moves to the lower or mark position. This condition corresponds to the start element of the message signal, and a circuit is closed through contacts KV2 to magnets Ml, MV which control the release of the transmitter device for the cipher key perforated tape, and of a distributer which opens contacts KV2 and by the periodic closure of contacts KV1 effects the timing of the operation of relay SR and the transmission contact sr of the combined, or ciphered signals applied at the contact mr of the relay MR. With the contact' mr in its lower position, the relay SR is operated by the circuit closed through the winding (5, 8) by contact KV1 to move contact sr to its upper position to open the line circuit. If the armature mr sticks on its upper contact, the relay remains in the condition with contact sr closed; and no signals can pass to the line L. If the armature mr remains fixed on its lower contact, the magnets M1, MV are energized maintaining rotation of the transmitter and distributer shafts, and' the periodic energization of the winding (5, 8) of the relay SR with no connection to the winding (1, 4) maintains contact sr permanently open. If the armature mr establishes simultaneous contact with its upper and lower contacts, the magnets M1, MV are operated and the closure of contact KV1 completes circuits simultaneously through the windings (1, 4)'(5, 8), but the current through the winding (1, 4) is arranged to be twice that through winding (5, 8) so that the armature sr remains permanently on its lower contact, and no signals pass to the. line L. The operation of the receiving arrangement, Fig. 2, is generally similar to that of the transmitter, the ciphered signals from the line L being applied by the contact er of a biased receiving relay ER to a combining relay MR receiving also the cipher key signals from contact SS so that the plain text signals set up by the contact mr operate relay SR which at contact sr controls the magnet EM of the receiving teleprinter. The armature mr in its lower position in response to the received start element (open line condition) operates magnets M1, MV as at the transmitter. In a modification, Fig. 3 (not shown), arranged for half-duplex working, i.e. transmitting or receiving being' possible, each station has a circuit generally similar to Figs. 1, 2, and is conditioned for transmission or reception by a two-way switch-which, in the position for reception, is effective to cut in the receiving relay (ER) and teleprinter magnet (EM), whilst in its transmitting position it connects a choke to simulate the impedance of the receiving relay. In further modifications, Fig. 4 (not shown), the relay MR has two windings one in series with the cipher contacts and the other in series with the plain text contact operated by a keyboard or automatic tape transmitter, whilst in Fig. 5 (not shown), the relay MR with solely set winding is included in the arm of a balanced bridge having in its conjugate arm a source of potential, and in two constituent arms the cipher key contacts (with a series resistor) and the plain text contacts in series with the teleprinter receiving magnet. In the modified arrangement, Fig. 6, for twoway telegraph traffic as in Fig. 3 (not shown), the multiple position of transmit-receive switch SU1, SU2, SU3 is in the position shown for reception and is moved to the opposite position for transmission from the keyboard, operating contacts HS. When message transmission takes place from perforated tape, the transmitter closes a contact S operating a relay U which at contacts u1, u2 switches the circuit to the transmitting condition and at contact u3 opens one of the circuits to the winding (3, 4) of a relay GR. Assuming that signals are being received from distant station with message transmission from its automatic perforated tape transmitter and the operator at the receiving station wishes to break in, he operates his key SU1, SU2, SU3 to the position opposite that shown and transmits signals from his keyboard. In addition to the mutilation of the signals being received, the line circuit is opened during the stop element period of the signal from the automatic transmitter at the distant station so that during this period windings (1, 2) and (3, 4) of relay GR are both without current since contact KV3 is opened during the stop period. Alarm relay A releases and at contact a1 opens its holding circuit. At contact a2 an alarm lamp AL is illuminated, and at contact a3 the contacts HS, LS are shortcircuited so that the automatic transmitter stops, allowing contact S1 to open with the consequent release of relay U. At contacts u1, u2 the transmitting station is conditioned for reception of a message from the distant operator. At contact u3 relay GR is operated, and after receiving the message, the operation of a key AT re-operates relay A which locks up over a1, extinguishes the lamp AL at a2, and removes the short circuit at a3 so that the circuit is ready to resume message transmission from the automatic tape transmitter. In further modifications, Figs. 7, 8 (not shown), comprising a transmitter and receiver respectively, and generally similar, the numbering relay (MR) is provided with a biasing winding and a second winding connected to diagonally opposite corners of a Graetz rectifier bridge. One of the other two corners of the bridge is connected to a circuit including the cipher key contacts. The other corner is connected, in the case of the transmitter, Fig. 7 (not shown), to the plain text contact in series with the magnet of the home or local teleprinter and, in the case of the receiver, Fig. 8 (not shown), to the contact of the line-receiving relay.