Patent GB-624693-A (GB)
Title: Improvements in or relating to printing telegraph apparatus
IPC: H04L15/34
Filed: 1946-02-21
Abstract: 624,693. Type-printing telegraphy. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Feb. 21, 1946, No. 5497. Convention date, Feb. 22, 1945. [Class 40 (iii)] A type-printing telegraph receiver responsive to an unequal length code (e.g. Morse) of the kind in which selection is effected by movement of one or more of a plurality of slotted code bars is characterised in that one bar is moved for a dot element and two bars for a dash element, the number moved being determined by the current condition in the second half of the first dot cycle of each signal element, a dot cycle being the period occupied by a dot plus its following equal-length space. The invention is described in connection with a start-stop type-printing receiver designed for Baudot type codes, as disclosed in Specification 245,149. The first half of the first dot-cycle of any signal received must be a mark. Upon the receipt of any letter (e.g. A), magnet 78 therefore immediately attracts its armature 77, Fig. 1, and its rear extension 81 brings a hook 82 into engagement with a trip-latch 83 to release a spring-loaded stop-lever 39 from a notch in clutch-member 19. A selecting shaft 20, Fig. 1, is therefore driven by the constantly rotating clutch-member 17 and rotates a cam-wheel 28 one of whose chamfered lugs 29, 30 comes opposite a rod 90 in the middle of the first half of each dot-cycle only. Shaft 20 also rotates a drum 43, Figs. 1 and 9, containing operating bars 44 pivoted on a fulcrum ring 45 and retained horizontal by a spring-loaded cap 46. Adjacent to part of the drum 43 is an arcuate platform 97 having at its front end a tiltable platform 99, the leading edge of which is normally depressed by a spring to form a ramp up which, as the drum 43 rotates, a projection 48 of the next bar 44 rides. As soon as this bar passes the pivot point of the ramp 99 the latter snaps back to its horizontal position, where it is retained by a catch 105, subsequent bars 44 passing beneath it. During the last half of the first dot-cycle the bar 44 riding along the platform 97 strikes the camprojection 53 on the first, or lowest, of ten selector bars 52. These bars are arcuate in shape and each has a depending arm with a projection 53 so arranged that the ten projections 53 are all in the plane of the bottom bar 52 and evenly spaced around its length. The projection 53 struck by the raised operating bar 44 moves its selector bar 52 upwards in Fig. 1 to rock a bell-crank 66 about its pivot 67 and retract an associated sword 70 from its T-member 114. Since for the letter A the second half of the first dot-cycle is a space, magnet 78 is now de-energized and arm 71 of the sword 70 will strike a downwardly depending prong 73 of the armature extension 75, and so rock the sword 70 down to the dotted position 144. Spring 68 of the selector bar is prevented from forcing the sword 70 back to the left, since the T 114 is locked by pins 126, 127. The operating bar 44 continues to move and passes the projection 53, forcing this back against the pressure of a leaf spring 60. The first half of the second dot-cycle would start shaft 20 rotating, but as this is already the case, nothing happens. During the second half of this cycle, a mark, the raised operating bar 44 strikes the second selector bar projection 53 and sets its associated sword 70 to the dotted position 144a. Similarly, the last half of the third cycle, a space, causes a third sword 70 to move down to the dotted position 144. Since the code signal for the letter A is now complete, the first half of the fourth cycle is a space and cam 29 (or 30) (Fig. 1) is opposite rod 90 and a trigger insert 89 is now placed between the two by the unenergized magnet 78. Continued rotation of the cam-wheel 28 moves rod 90 to the right and by means of lever mechanism rocks the stop lever 39 to stop cam member 19 and the selecting shaft 20 and at the same time via levers 38, 31 to allow the clutch-driven printing assembly, cams 5 and 6 and gear 8 to rotate. Cam 5 allows rod 125, Fig. 2, to move to the right and a spring 127a urges a slide 119, bearing the stop pins 126, 127 to the left to release the T-members 114, Fig. 1, the first and third of which are now turned clockwise and the second counterclockwise by swords 70 urged to the left by springs 68. The T-members move corresponding code-bars 116 up or down so that an alignment of slots is presented for a particular pull-bar 117, the unmoved code-bars 116 (4 ... 10 for the letter A) being slotted opposite this pull-bar. Cam 6 by means of suitable linkage pushes platform 97 outwards and releases the raised operating bar 44 and also catch 105 which allows the ramp 99 to tilt again. The gear 8 drives a printing-cam 130 whose follower 131 allows a spring 136a to raise a lever 134 and a printing-bail plunger 138, Fig. 2, whose catch 142 engages a hook 143 of the pull-bar 117 which has fallen into the aligned notches of the code-bars 116. Printing of the letter A then takes place as in Specification 245,149, [Class 40 (iii)]. Cam .5 then returns the slide 119 and again locks the T-members 114 in their neutral position ready for the next code-signal.