telegraph system and automatic correction of errors in observation

摘要

912,252. Error-correcting telegraph systems. DE STAAT DER NEDERLANDEN, TEN DEZE VERTEGENWOORDIDG DOOR DE DIRECTEUR-GENERAL DER POSTERIJEN TELEGRAFIE EN TELEFONIE. Feb. 6, 1961 [Feb. 1.5, 1960], No 4368/61. Class 40 (3). A two-way telegraph system in which signals found to be faulty upon reception are corrected by repetition is characterized in that when one station detects an error it transmits to the other station a series of service signals requesting repetition until a similar service signal is received from the second station. When a service signal is received by a station either a repetition cycle is initiated, i.e. transmission of data stops and a service signal is transmitted followed by a repeat of previously transmitted data, or, if the station is currently transmitting repetition requesting signals, a further service signal is transmitted followed by either a repeat of previously transmitted data or by the next in order data signal to be transmitted, depending upon the read-out position of an associated store. The repetition cycle is of four data signals' length, and is always completed, even if a service signal is received during the cycle. In one example, Fig. 1, stations P and Q each comprise a transmitter Z and a receiver O. If signal A is faulty upon reception the receiver printer of Q is blocked for four cycles, indicated by 1, 2, 3, 4 and Q transmits a series of service signals I, the transmission of data being stopped. When station P receives a signal I its printer is blocked for four cycles and it transmits a signal I indicative of the start of a repetition cycle. As Q is currently transmitting repetition requesting signals when this latter signal I is received, Q transmits a signal I followed by data signal a, b, c ... in the case of a transmission path of 140 msec., or followed by a repeated data signal z and signal a, b, c ... in the case of a transmission path of 70 msec., Fig. 3 (not shown). The division of the data signals into groups of n signals by polarity inversion of a certain one out of each n data signals is mentioned. Specification 693,211 is referred to.