Patent GB-318841-A (GB)
Title: Improvements in or relating to telegraph systems
IPC: H04L25/04
Filed: 1928-03-06
Abstract: 318,841. Marks, E. C. R., (Western Union Telegraph Co.). March 6, 1928. Automatic telegraphy; translating from one code to another.-Wheatstone morse signals are applied to the transmitter and taken from the receiver of a cable telegraph system, while the currents in the cable itself conform to a modified cable morse code. The invention is based on the fact that everv Wheatstone morse letter can be regarded as made up of a number of pairs of current impulses, e.g., the letter A followed by a letter-space mav be regarded as + -,++, + -, - -, in Wheatstone morse, and according to one form of the invention it is transmitted as + - + 0 in the line. In the example shown, a tape punched in Wheatstone morse is applied to the transmitter T; in the cable, a dot is represented by a positive impulse a, Fig. 7, a dash by a negative impulse b followed by a positive impulse c, and a space by a zero current d; while at the receiver the armature 40a of the regenerating relay 40 is set according to Wheatstone morse code, as indicated in Fig. 6. Transmitter. The feelers 21, 22 rise simultaneously through the pair of dot holes e, Fig. 1, so that for a dot the relays 11, 12 are both energized. The armature 14 is, however, disconnected irom line by the downward, movement of the armature 13, which sends a positive impulse a to line from the battery 13a. During the next time-unit the feeler 22 rises alone through the first dash hole f, so that a negative impulse b goes to line from battery 14a through armature 14. During the next time-unit the feeler 21 rises through the second dash hole g, and a positive impulse c goes to line in completion of the dash. During the next time-unit neither feeler rises, and the cable is earthed at 16, so that there is zero current d in the line. Regenerator. The positive dot impulse causes the receiver coil 23 to move its contact 24 to the left; the dot relay 25 therefore operates to close a circuit through the segment 1 of the dot ring 33, brush 41, dot looking relay 39 and regenerating relay 40, which registers a positive impulse over the armature 40a. The latter impulse is held on by the second segment 1A of the dot ring but the third and fourth segments are idle, so that when the brush is passing over those segments the regenerating relay registers a negative impulse under the influence of the spacing winding 46. The dot is therefore registered by the armature 40a as a pair of impulses WW, Fig. 6. The negative part b, Fig. 7, of the incoming dash then moves the armature 24 to the right; the dash relay 26 consequently operates the dash locking relay 57 and regenerating relay 40 via the segment 2 of the dash ring 49. All three segments 2X, 2Y are connected to the locked armature 57a so that a full time positive impulse XX, Fig. 6, is registered by the armature 40a. The positive part c, Fig. 7, of the incoming dash signal acts like a dot through the relay 25, causing the armature 40a to register the elements Y, Y, Fig. 6, while the incoming space signal d leaves the coil 23 in its middle position so that a negative outgoing current ZZ is registered. The letter A and space are thus converted from the modified cable code Fig. 7, to the Wheatstone. code, Fig. 6; both signals occupy the same time, but the shortest timeelement in Fig. 7 is twice as long as that in Fig. 6 The Specification refers to the method of high speed telegraphy described in Specification 9768/13, and also to a known mechanical arrangement for translating from one code to another.