| 摘要 |
A method and apparatus is disclosed for detecting the frequency to which a broadcast receiver is tuned. In one embodiment, a sensing unit emits a chirp signal over a range of broadcast bands and monitors the output of the radio receiver to detect the frequency to which the radio receiver is tuned. In another embodiment, a sensing unit demodulates radio signals across a range of frequencies and compares the demodulated signals to observed audio output of the radio receiver.
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