GB519633A - Printing telegraph system - Google Patents

Abstract

519,633. Type-printing telegraphy. DUUREN, H. C. A. VAN. Sept. 24, 1938, No. 27913. Convention date, Sept. 25, 1937. Drawings to Specification. [Class 40 (iii)] In a printing telegraph system using code elements of different character, the ratio of the number of elements of each character representing each letter &c. is constant and the receiver is so arranged that upon receipt of a signal wherein the said ratio of elements is incorrect the printer is unaffected by the received signal and the receiver automatically sends to the transmitter signals to cause the retransmission of the signal which was received incorrectly. The invention is described as applied to an eight-unit code consisting of four positive and four negative impulses. For transmission the normal five-unit code is translated into the eight-unit code by the addition of one, two or three impulses of appropriate polarity. Those combinations of the five-unit code having five similar impulses are translated into combinations having the last three impulses of a characteristic form. At the receiver those combinations having the correct proportion of positive and negative impulses are passed to a printer, the last three impulses being suppressed except that in the two cases where it is necessary the combination is translated into the fiveunit code before passing to the printer. If a signal is received in which the elements are not in the correct ratio, relays operate to send a warning signal back to the transmitter. When the transmitter is tape operated such a warning signal causes the automatic stepping back of the tape so that the mutilated signal is retransmitted. Specification 419,526 is referred to.