GB543590A - Improvements in or relating to apparatus for producing audible signals - Google Patents

Abstract

543,590. Signalling by audible signals. COMPTON ORGAN CO., Ltd., J., and FAIR. W. T. H. Aug. 31, 1940, No. 13682. [Classes 40 (i) and 118 (ii)] Apparatus for producing audible signals, particularly air-raid warnings, comprises an electric sound generator rotated by a motor, and means for alternately energizing and deenergizing the motor thereby varying the speed of the generator and producing a note of undulating pitch. The generator may be of the kind described in Specifications 403,444 and 433,050 in which a number of rings are employed to generate undulating electric potentials. The generator is rotated by an electric motor 4 and is connected to a source of potential 2 and one or more loudspeakers 3. The motor is connected to a source of power 5 through a throwover switch with two sets of contacts one of which, 8, is connected to the motor by leads 6, 7. When the contact is closed, the motor rotates at a steady speed and the " all clear " signal is given by the loudspeaker 3. The contacts 12 are connected to the motor by leads 9, 11, and contacts 10 which are opened and closed intermittently to vary the speed of the motor to give the "take-cover" signal. This is effected by a centrifugal governor 13, on the shaft of the motor, which is provided with a disc 14 that moves axially along the shaft. The disc oscillates a pivoted arm 15 which is connected by a blade spring 19 with another pivoted arm 16. One end of the arm 16 operates the contacts 10, and the other end is provided with a stop 21 that engages a stop 20 on the arm 15. In operation, when the contact 12 is closed, the speed of the motor increases and the arm 15 is rocked. At a particular speed, the stop 20 moves clear of the stop 21 and the spring 19 moves the arm 16 to a position at which it opens the contacts 10. The speed of the motor then decreases until the stop 20 has again moved clear of the stop 21 when the spring 19 moves the arm 16 to a position at which the contacts 10 are closed. If desired, the contacts 10 may be replaced by a mercury switch mounted on the arm 16. A multi-pole switch 23 may be provided to enable any generator ring, or selection of rings, to be connected to the source of potential 2 so that any tone pitch may be produced. The sound produced may ' be made intermittent, for " imminent peril" warnings for example, by operating a pair of contacts 26 by a rotating cam 27. A number of cams may be used to repeat a given cycle of tone pitches, and according to the Provisional Specification the device may be arranged to transmit Morse signals.