GB177488A - Improvements in electrical selective calling devices - Google Patents

Abstract

177,488. Soc. Franþaise Radio-Electrique. March 22, 1921, [Convention date]. Electric selectors.-Comprises a selector for closing a call circuit on receipt of a Morse or like train of impulses, in which a member, such as the core 2 of an electromagnet 1, tends to close the call alarm circuit but is normally restrained by the energization of the magnet. On receipt of impulses, the member 2 is released, but can only complete its action provided that the received train of impulses coincides in its character with the spacing of a set of contactmakers 10. In the form shown, the core 2 tends to fall by its own weight against the action of a return-spring within the drum 4. The descent is controlled by a fly 9, a ratchet 7 being provided to make possible a quick return of the core; or by a dash-pot, oil-brake, free-wheel or the like. The electromagnet 1 is normally energized and helps the return-spring to keep the core 2 in its uppermost position, as shown, but a line-impulse causes the relay 13 to break at 15 the circuit of the electromagnet. The core 2 begins to descend, the return spring being too weak to sustain its weight alone, and if the call is that of the station in question the shoulders 10 on the core energize the relay 12 during the intervals between the line-impulses, so that the circuit of the magnet 1 is always broken either at 14 or at 15, and the shoulder 21 eventually closes the alarm-circuit at 16. If, however, the magnets 12 and 13 should be simultaneously energized or simultaneously de-energized owing to want of correspondence between the received signal and the spacing of the shoulders 10, the magnet 1 is again energized and the core 2 rises. To ensure that a further call shall not be effective during the ascent of the core, a hold-on circuit 19 is prepared at 18 by its descent. In a modification, the core may be replaced bv a rotary member. This hold-on circuit becomes effective at the same time that the magnet 1 is energized, and is only broken at 21 on completion of the ascent. The device may be re-set manually or automatically. The part 10 may be replaceable to adapt the apparatus for different calls.