Patent GB-235193-A (GB)
Title: Method of and means for avoiding parasitic interference due, for example, to atmospherics in telegraphic systems employing synchronised transmitters and receivers, more particularly in wireless
IPC: H04L1/08
Filed: 1925-06-04
Abstract: 235,193. Verdan, C. E. June 4, 1924, [Convention date]. Atmospherics and undesired signals, climinating or limiting.-Relates to systems of telegraphy employing the Baudot or like code and comprises an arrangement whereby interference due to atmospherics and like disturbances is avoided. In the example, illustrated each combination of five elements representing a given letter is sent three times, at intervals such that an atmospheric which interferes with one of the three emissions is not likely to interfere with the others; and a given element will not be recorded unless a positive signal has been received at all of the three instants corresponding to it. Receiver. The developed rings F, E represent the ordinary rings of a Baudot receiver, the ring E being continuous while the ring F has three sets of five segments T1 - - T15 accompanied by synchronizing segments T16, T17. These seventeen segments are repeated three times in the drawing to represent three successive rotations of the brushes a. The brushes b and c make one revolution during the above three, and all brushes move from left to right in the drawing. The output of the receiver relay R is connected to all the segments of the ring F, and the brushes a connect these segments to the ring E, which is permanently connected to the ring B, the effect being that the relay R is connected directly to the brushes b and so in succession to the fifty-one segments of the ring A. The latter are connected to three groups of magnets X, Y, Z, dealing with successive letters in such a way that three successive letters are printed as the brushes b pass over the three groups of contacts 1 - - 5 of the three sets. The groups X. Y, Z of magnets are similar to one another. In the group X the segments 46, 47 are for synchronizing purposes while the remaining fifteen segments fall into three groups of which 11 - - 15 receive the first. 6 - - 10 the second, and 1 - - 5 the third and final group of signals representing each letter. Thus the segments 11 - - 15 are directly connected to the magnets X11 - - 14, so. that if, for instance, the letter A (+, 0, 0, 0, 0) is being sent when the brushes b are passing over these segments the magnet X11 will be energized, locking itself at III and preparing at M6 the circuit of the magnet X6. The letter will be sent again when the brushes b are passing over the segments 6 - - 10 the next time, the segment 6 receiving a signal, so that the magnet X6 becomes energized, locking itself at 16 and preparing at M1 the circuit of the printing magnet L1. Immediately afterwards the brushes c clear the magnet X11, by earthing the segment 11, and this magnet is ready to receive the first signal for another letter from the brushes b, the original letter A being meanwhile stored in the magnets X6 - - X10. The next time that the brushes b pass over the segments 1 - - 5, the letter A will be received for the third and final occasion and the printing magnet Ll will operate, since an impulse will be received as the brushes b pass over the segment 1. Immediately afterwards the brushes c will earth the segment 6a, clearing the magnet X6 ready for a fresh signal, the segments 6a - - 10a being respectively connected to the contacts 16 - - 110 as indicated in the drawing in the case of 10a, I10 onlv. Transmitter. The above apparatus can be adapted for use as a transmitter by substituting the apparatus and connections shown in Fig. 6 for the corresponding parts shown in Fig. 5. In the keyboard M the key for, e.g. the letter A (+, 0, 0, 0, 0) is depressed, the contact T11 being energized while the contacts T12 - - T15 are not. When the brushes a, b reach the segments T11, a circuit is closed from the battery P1 through the transmitting relay R, Fig. 6, and through the magnet X11, Fig. 5, to earth, and the letter A will consequently be emitted for the first time, the magnet X6 being meanwhile prepared at M6 by energization of the magnet X11. The contacts T1 - - T10 being permanently energized as shown, at the next revolution of the brushes b a circuit including the relay R will be closed through the magnet X6, the second emission of the letter A being thus effected while the armature M1 is prepared, by energization of the magnet X6, for the third and final emission, which occurs when the brushes b next reach the segments 1, Fig. 6. The magnets are cleared by the brushes c as in the case of the receiver.