| 摘要 |
<p>A radio receiver for receiving audio frequency communications conveyed by a high-frequency carrier and occurring randomly over time. In addition to the tuning circuits (1), a detector (2), audio frequency amplifier means (4) and a sound transducer (5), said receiver includes controlled switching means (3) connected between the detector (2) and the amplifier means (4) for disabling or reenabling the transfer of the audio signal from the detector (2) to the sound transducer (5). Filtering and detection means (12, 13) set a silence threshold to provide squelch. The means are arranged to set the silence threshold in accordance with the level of a part of the audio spectrum from the detector (2) of which the frequency band only contains noise and is located outside the frequency band of the signal representing the useful audio communication to be received. Said receiver is particularly suitable for use in citizen's band equipment.</p> |
