Patent GB-308672-A (GB)
Title: Improvements in or relating to electric telegraphic receiving apparatus
IPC: H04L7/00
Filed: 1927-12-24
Abstract: 308,672. Creed & Co., Ltd., Creed, F. G., Salmon, R. D., and Kirk, S. E. Dec. 24, 1927. Synchronous movements.-In a telegraph receiver of the kind which is kept in phase with incoming signals by being caused to run alternately at two different fixed speeds, one of which is slightly faster and the other slightly slower than the speed of the transmitter, the appropriate speed is selected by mechanical means at each change in the polarity of the signals. Speed-setting device for use with 5-unit code or land-line morse, Figs. 1, 8. The speed is selected by the lever 11 which is pivoted at 11<a> and is moved against its upper stop 12 or lower stop 13, as required, by co-operation between (a) the hammer 9 carried by a. bell-crank lever 7 which is reciprocated in synchronism with the receiver shaft A by the cam 6a and (b) an escapement device, moved in synchronism with the incoming signals, which comprises a disc 15 driven frictionally from the continuously rotating shaft 18<a>, the disc being normally held against rotation by engagement of a projection 19 thereon with a catch 20<a> or 20<b> and released for half a rotation whenever the plate 20, which carries the catches, is moved in one direction or the other about its pivot 20c by the magnet 22 through linkwork 22a, 21 upon a change in the polarity of the signals. At each half-rotation of the disc 15 a cam-shaped projection 15a or 15b thereon drives the hammer 9 to the right, Fig. 1, and if the horizontal movement of this hammer (which is synchronous with the incoming signals) is sufficiently out of phase with its vertical movement (which is synchronous with the receiver shaft) it strikes one or other of the bevelled surfaces 10 of the lever 11 so as to shift the lever and change the speed. Alternatively the engaging parts may both be V-shaped points (Fig. 4, not shown). Speed-setting device for use with cable code. In a modification (Fig. 10, not shown) the hammer 9 is adapted to be moved forward by either of two bell-crank levers which take the place of the plate 15 and are actuated under the control of two escapement mechanisms governed respectively by the dot and dash magnets. Alternatively, the hammer may be moved forward by the armature 34<a> Fig. 13, of a magnet 34 which is energized by the discharge of a condenser 35 every time the armature 33a of the polarized relav 33 closes the circuit of the dot or dash magnet 29 or 30. Selection of speed by speed-setting device. The two speed-governors of the receiver, which are set respectively to a speed slightly above and a speed slightly below the transmitter speed, may be of the kind described in Specification 292,210, [Class 57, Governors &c.]. The arrangements are such that in one position of the speed-setting lever 11, Fig. 1, the fast governor only is in circuit (Fig. 2, not shown) while in the other position both governors are in circuit; in the latter circumstances the fast governor is ineffective and the slow governor takes control. Clutches and escapements. In another arrangement, Fig. 14. the receiver shaft A is driven from the motor shaft A<1> through one or other of two coil clutches. When the friction disc 53 is rotating in engagement with the pinion 46, the shaft A is directly driven from the shaft A<1> through the coil clutch 45, but when the disc 53 is held by the lever 53b the driving takes place through the reducing gear 47, 48, 49 and coil clutch 51, so that the shaft A runs at a slightly slower speed. 'The speed-selecting lever 53b is actuated by the magnet 54 under control of the lever 11. The clutch and escapement device described above (comprising a. friction disc 15, Figs. 1 and 8, which is normally held by the detents 20a, 20b, but is driven for half a revolution by the shaft 18a upon each movement of the plate 20) may be replaced by a similar arrangement (Figs. 10, 11, not shown) in which the frictionally engaging parts are cylindrical.