Patent GB-606156-A (GB)
Title: Improvements in or relating to selector apparatus
IPC: H04L17/18
Filed: 1946-01-23
Abstract: 606,156. Party - line telegraph systems. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Jan. 23, 1946, No. 2250. Convention date, Jan. 24, 1945. [Class 40 (iii)] [Also in Groups XXXVII and XXXVIII] A selector which performs an operation in response to a plurality of signal controlled selectable orientations of a shaft is so arranged that the receipt of each correct element of a signal combination causes a cam to rock a corresponding cam-follower lever about a digital projection of a related disc mounted on the said orientable shaft, the cam-follower lever moving a respective pawl-lever to advance a ratchet assembly by one step. As described the selector requires a combination of two codesignals in order to operate correctly. Incoming code signals, differentiated by length, are received by a start-stop translating device which clutches a continuously rotating motor (not shown) simuitaneously to two shafts 1 and 2. At the end of a first signal the rotation of the shafts ceases, but if the signal is correct it will have positioned a digital projection 3<1> of a disc 3 beneath a finger 26b of a camfollower lever 26, and a notch in a disc 5 beneath a finger 18c of an operating lever 18. The other shaft 2 rotates more slowly so that by the time a cam 23 comes beneath its cam-follower 25 shaft 1 will be in the position described above. The cam-follower lever 27 then merely pivots about a shaft 49 on lever 19, but soon afterwards cam 22 lifts its own follower 25 to tilt its lever 26 clockwise about the fulcrum formed by the finger 26b resting on the projection of disc 3. The operating lever 18 is therefore rotated clockwise about its pivot 20, finger 18c entering its associated slot in the disc 5, and drives a spring-loaded pawl 13 to the left to advance a twin-ratchet assembly 8, 9 by one step, in which position it is retained by a second pawl 14. The shafts 1 and 2 are now de-clutched and return to their homing positions ready for the next signal, receipt of which again causes them to rotate and if the signal is correct, positions the projection on a disc 4 and the notch on a disc 6 beneath fingers 27b and 19c respectively before cam 23 lifts its cam-follower 25, and tilts lever 27 clockwise about the fulcrum formed by finger 27b resting on the, projection of disc 4 tilting operating lever 19 clockwise about its pivot 20 and driving pawl 14 to the left to advance the ratchet assembly another step, in which position it is retained by a holding pawl 31. In this position a ratchet extension 43 closes contacts 45 to operate for example a magnetic clutch, motor, bell or indicator, or the ratchet may actuate any desired device mechanically. The selector is re-set upon the receipt of a special single signal which rotates the shaft 1 until a cam 7 thereon rocks a bell-crank 37 to move a rod 35 to the left. When the shaft 2 subsequently causes a cam 21 to depress a rod 40 the latter now depresses the end of the rod 35 and hence moves the holding pawl 31 out of engagement with the ratchet 8. At this instant cam 23 will rock the cam-follower lever 27 about its pivot 49 and thus kick the pawl 14 clear of ratchet 9, which will return until the associated ratchet 8 is engaged by the pawl 13. Further rotation of the shaft 2 causes cam 22 to rock lever 26 and kick pawl 13 clear so that ratchet extension 43 comes to rest against a stop 44, and the ratchet assembly is ready to advance again upon receipt of a suitable signal. When a selector has been partly operated by a first signal and then receives an incorrect second signal cam 23 rocks its follower lever 27 about its pivot 49 and kicks pawl 14 clear of ratchet 9. The ratchet assembly therefore restores to normal. In order that all receiving selectors may operate simultaneously to a special signal the discs 3, 4 have a second projection arranged in a position, or positions, common to all receivers and the discs 5, 6 similarly have a second notch. By adding extra discs on shaft 1 and associated levers and cams, the selector may be made to operate only upon the receipt of more than two correct signals.