Patent GB-308734-A (GB)
Title: Improvements in telegraphic systems
IPC: H04L7/00
Filed: 1929-03-27
Abstract: 308,734. Verdan, C. E., (Assignees of Ateliers, J. Carpentier). March 27, 1928, [Convention date]. Addition to 235,193. Eliminating effects of disturbing currents; synchronous movements.-The method of eliminating the effect of atmospherics described in the parent Specification is applied, according to the present invention, to the system by which a Baudot or like receiver is kept in synchronism with the transmitter; synchronizing impulses have no effect on the receiver until three have been registered in succession. The system described is of the following hind : The receiver runs slightly faster than the transmitter, synchronizing impulses are sent out once per revolution of the latter, and the receiver brush is periodically stepped back through a finite angle in response thereto. Fig. 1 shows schematically the synchronizing distributor at the receiver. If the distributor brush be at a immediately after correction by a synchronizing impulse, the brush will gain slightly during the next five revolutions so as to occupy the positions a, b, c, d, e, f at the instants when succeeding synchronizing impulses are received upon the distributor segment 10. The first two of these impulses have no effect, since in the positions b, c the brush is out of contact with the segment. The next two impulses prepare the correcting apparatus and the third, received by the brush when in the position f, applies a backward phase correction e so that the brush jumps back to the position a and then continues to rotate. Atmospherics fail to effect this correction except in the improbable event of three atmospherics occurring in succession at the requisite intervals of time. The brush h, Fig. 2, at each revolution bridges the contacts 11 and so applies current from the battery B via the switch 5 to the magnet 2 if the armature 14 is in the de-energized position shown, or to the magnet 3 if the armature 14 is in the energized position, the middle spring of the switch 5 being then to the right. So long as no synchronizing impulses are being registered, the armature 14 is locked in the energized position by the armature 13 of the magnet 1, so that all the impulses applied by the contacts 11 pass to the release magnet 3, and the rack 7 is pressed to the right by the spring 19. When, however, a received impulse effects a connection between the line terminals 18 simultaneously with the passage of brush g over segment 10, magnet 1 is energized and armature 14 is unlocked and allowed to fall to the position shown. The switch 5 is thus so set that magnet 2 instead of magnet 3 is energized at the next revolution via contacts 11 and moves the rack 7 one step to the left, the pawl 8 disengaging itself from the rack after each movement. If a second impulse arrives at the next passage of brush g over segment 10, this operation is repeated and the rack 7 is moved a further step, so that the middle contact of switch 6 moves to the left. If not more than two incoming impulses take effect over terminals 18 and segment 10, the magnet 3 releases the rack 7 at the next revolution, but if a third impulse arrives at the right moment it passes not through the magnet 1 but via the left-hand contact of switch 6 through the synchronism correcting magnet 4, which effects the required backstepping of the distributor brushes. The pawl 8 engages the rack 7 only during movement, a counter-weight 17 and spring being provided to ensure engagement. In its extreme right and left positions the pawl is disengaged by the pins 16, 15, Fig. 3, which act upon the projections shown. A mechanical arrangement may take the place of the battery B.