HANDS-FREE CAR ADAPTOR FOR MOBILE TELEPHONES WITH BUILT-IN FM TRANSMITTER, IN WHICH FUNCTIONS ARE CONDITIONALLY ACTIVATED ACCORDING TO THE FREQUENCY MATCHING STATUS IN RELATION TO THE FREQUENCY OF THE ASSOCIATED RADIO SET

摘要

According to the invention, the device (10) relays signals from an audio source to a radio set, such as a car radio. The device comprises: means for producing a reference signal, means enabling the radio signal to be modulated by the reference signal or by the audio signals received by the coupling means, a microphone (20) for capturing acoustic signals present in the environment of the device, and means for analysing the acoustic signals captured by the microphone. When the user wants to activate a functionality, for example to transmit a call, the device executes an algorithm for detection of a known signal in a noisy environment, in order to determine the presence or absence of the reference signal in the acoustic signals captured by the microphone. When the reference signal is present in the captured acoustic signals the device effectively activates the functionality and when the reference signal is absent from said acoustic signals the device disables the functionality and activates an audible (22) and/or visible (30) alarm intended for the user.