ii extracting a video program signature from the program signal iii extracting an audio ancillary code from the program signal and iv extracting a video ancillary code from the program signal any one or more of these detection functions may be used in order to identify the local source of the signals displayed by the television receiver 22 u2032 for example the tuner of the television receiver 22 u2032 may be identified as the source of the signals being displayed by the television receiver 22 u2032 if a reference audio signature extracted from an audio output of the television receiver 22 u2032 matches a source audio signature extracted from an audio output of the source scanning tuner 66 or if a reference video signature extracted from a video output of the television receiver 22 u2032 matches a source video signature extracted from a video output of the source scanning tuner 66 similarly the vcr 28 may be identified as the local source of the signals being displayed by the television receiver 22 u2032 if a reference audio signature extracted from an audio output of the television receiver 22 u2032 matches a source audio signature extracted from an audio output of the vcr 28 or if a reference video signature extracted from a video output of the television receiver 22 u2032 matches a source video signature extracted from a video output of the vcr 28 the game 26 may be identified as the local source of the signals being displayed by the television receiver 22 u2032 if a reference audio signature extracted from an audio.