GB604923A - Combined radio and audible warning device - Google Patents

Abstract

604,923. Detecting approach of overtaking vehicles. SOC. ANON. A. CITROEN. April 3, 1945, No. 8238. Convention date, Feb. 15, 1944. [Class 118 (ii)] A vehicle warning system comprising an audible warning device equipped with a diaphragm and in association therewith an electromagnetic wave transmitter is characterised by the feature that the physical phenomena which produce vibrations of the said diaphragm or the vibrations themselves are utilized to modulate the high-frequency current of the electromagnetic wave transmitter. In the embodiment of Fig. 1 the ignition coil 2 supplies high-frequency currents to the sparking- plugs 6 and also to an aerial transformer 8. The radiated frequency is modulated by a vibrating contact 10 operated by the vibration of the diaphragm of the vehicle's audible warning device. The contact 10 may be integral with the interrupter of an electromagnetic horn and arranged to open when the interrupter contacts close. The modulating contact 10 may be shunted across the aerial transformer 8, Fig. 2 (not shown). In a further embodiment, Fig. 4 (not shown), an oscillatory circuit is connected across the interrupter contacts themselves, operation of the vehicle horn producing an oscillatory current which is fed to an antenna. In a further embodiment, Fig. 3 (not shown), the audible warning device is arranged to interrupt the primary ignition circuit, in addition to the normal interrupter, thus modulating at audio-frequency the hightension current in the ignition secondary circuit, which is coupled to an aerial.