Patent ID: 7359687

Claim:
An apparatus for detecting the tuned station of a radio tuner connected to an antenna and a speaker, comprising: a directional coupler that is coupled in between the antenna and the radio tuner; a modulator coupled to said directional coupler; a processor connected to said modulator and coupled between the radio tuner and the speaker; said modulator comprising: an FM code modulator for generating a coded signal having a pre-determined FM modulation frequency; an AM code modulator for generating a coded signal having a pre-determined AM modulation frequency; an FM synthesizer for creating an FM test signal by generating an FM carrier frequency signal corresponding to an FM station under test and receiving said coded signal injected into said carrier frequency signal by said FM code modulator, and capable of injecting said FM test signal into the radio tuner via said directional coupler; and an AM synthesizer for creating an AM test signal by generating an AM carrier frequency signal corresponding to an AM station under test and receiving said coded signal injected into said carrier frequency signal by said AM code modulator, and capable of injecting said AM test signal into the radio tuner via said directional coupler; and said processor comprising: a code correlator for analyzing signals received from the speaker output of the radio tuner to determine whether said FM or AM coded signal is recoverable from said received signal, thereby indicating the radio tuner is tuned to said FM or AM station under test.