Security device for forced entry-theft warning device for automobile detecting resonance variations of resonance space containing siren for activation of siren

摘要

The security device has a sensor (8) which monitors the region between a siren (1) of the forced entry-theft warning device and the walls (4,4a,4b) of the resonance space (3) enclosing the siren, for detecting resonance variations for activation of the siren. The sensor can be provided by an ultrasound sensor used for distance detection during driving of the automobile.