Patent GB-227133-A (GB)
Title: Improvements relating to the distant synchronising and releasing of apparatus to which a circular movement is imparted
IPC: H04N5/04
Filed: 1925-01-05
Abstract: 227,133. Etablissements E. Belin. Jan. 5, 1924, [Convention date]. Electric clocks; pendulums, regulating electrically.-Relates to means for ensuring isochronism and synchronism of two pendulums such as those controlling the transmitting and recording drums of copying telegraph apparatus. The pendulums, adjusted to approximate synchronism, are set in motion and, according to one arrangement, that at the transmitting station is arranged to send at each beat an impulse to an oscillograph at the receiving station, thus directing a spot of light to produce a succession of marks on a sensitized surface on the receiving drum. If the drums are not moving isochronously these marks are in a line such as d, Fig. 1, inclined to a generating line of the receiving drum, and the length of the pendulum at the receiving station is adjusted until the line extends along a generating line as shown at g. To bring the drums into synchronism the pendulum at the receiving station is similarly connected to the oscillograph to produce a similar line on a generating line of the receiving drum, and the contact controlled by the pendulum at the receiving station is adjusted to bring the two lines on to the same generating line. Each pendulum comprises a rod A, Fig. 2, of wood injected with linseed oil, carrying a weight X and mounted on a knife-edge C carried by a screw V<1> for adjusting the length of the pendulum. To enable the two pendulums to be released simultaneously each is provided with a stop D<2> arranged for engagement by a heok on the armature of an electromagnet, switches being provided to enable such electromagnets to be energized simultaneously over the line. The closure at each beat of circuits for effecting the release of the corresponding drum and for transmitting the successive test impulses to the oscillograph is effected by the engagement of an adjustable stylus S, Fig. 3, by an adjustable finger D' on the pendulum, thus opening a normally-closed shunt to these circuits. Fig. 4 shows another arrangement for obtaining correspondence of movement of the two pendulums, particularly suitable when the transmission is over a telephone circuit. A disc 7<1> on the motor-driven shaft to be controlled is released periodically by an impulse from a chronometer 1<1> through a relay R controlling the releasing magnet 4<1>, and the rheostat controlling the motor speed is adjusted to make the period of arrest of the shaft a minimum. Switches H, K are then moved to position 2 to enable the beat of the chronometer to be heard in the telephone E, and, the key M being on its stop, test signal beats due to the engagement of a contact 9 on the dies 7<1> with a contact 10<1> on an adjustable crown 12 are also heard in the telephone, and the crown may be adjusted to bring the two sets of beats into coincidence to verify the isochronism of the disc 7<1> with the chronometer 1<1>. The switch H is then moved to position 1 to enable test signals, produced at the passage of the pendulum at the other station through the vertical, to be heard in the telephone and the crown 12 is adjusted to bring the test signals at both stations into coincidence. The two pendulums are then brought into exact synchronism by releasing the local pendulum at an instant midway between two successive test signals. For this purpose the crown 12 carries, diametrically opposite the contact 10<1>, a contact 10<2>, which, when the key M is pressed, co-operates with the contact 9 to close the circuit of the release magnet D.