Patent GB-833096-A (GB)
Title: Improvements in or relating to teleprinter transmission systems
IPC: H04L12/00
Filed: 1957-11-06
Abstract: 833,096. Code telegraphy. SIEMENS & HALSKE A.G. Nov. 6, 1957 [Nov. 6, 1956], No. 34626/57. Class 40 (3). A teleprinter system having two successive transmission channels is provided with means located at the junction between the two channels for automatically transmitting over the first channel a predetermined code combination, which does not operate the teleprinter receiver, if a message passed over that channel is delayed in onward transmission over the second channel. When a call is initiated the switch members AT1, AT2 are operated to the dotted line positions and relay F is operated over AT1 or the contact sr of sending relay SR in the rest position Z. When the connection has been established the switch contacts AT1, AT2 are operated to their full line positions and the relay F is held operated by capacitor C1 during or at the end of normal teleprinter communication. The junction position between a teleprinter line L and a connection UeS to a radio link may include a reperforator and a tape transmitter in which the feeler contact pk is in the position shown when the current message traffic has been forwarded, and in the opposite position when message transmission is taking place. If the calling subscriber desires a reply from the distant subscriber he opens his line so that contact sr is on the spacing contact T, and if no answer is received after a predetermined time, e.g. ten seconds, the relay F releases and over contact pk (lower position) g2, f1 (released) and AT2 (normal), the relay E is energized. At contact e1 a circuit is completed for the winding II of relay St and at contact e2 in series with contacts operated by transmitter ZZG during the period of the stop element, the relay NK operates and at contact nk1 completes a circuit for the winding I of relay St. A circuit is completed for the winding I of relay R which operates, and at contacts r6 connects to the calling subscriber a transmitter ZZG which sends the all-blank signal providing an indication that the system is operative, but that arrears of message traffic exist at the junction position. At contact r2 a holding circuit, independent of contacts nk2, st2, is completed for relay E. At contact r1 a relay G is energized and over contact g2 opens the original circuit of relay E, which is temporarily held over contact e3 and r2 or nk2. If the transmitter ZZG again operates relay NK during the stop pulse, the winding II of relay R is energized in the reverse direction so that the relay releases. At opened contact r2 relay E releases since contact nk2 is opened, and after a fixed time, e.g. four seconds, relay G releases so that the relay E can be re-operated and the advisory signal repeated, if the contact pk is still in the position opposite that shown. If the delay is due to faulty reception at the distant station which sends the RQ signal requesting repetition, the contact w1 at the junction position is closed to initiate the transmission of the advisory signal when relay F releases, and the signal is repeated when the contact w1 is again closed after an interval of four characters, i.e. approximately ¢ second.