| 摘要 |
<p>The audio passband regulator has an audio frequency low-pass filter whose cutoff frequency coincides with the upper limit of the receiver's passband. The filter is connected at its input to the output of the receiver's detector and at its output to the receiver's audio circuitry. A control circuit receives signals from sensors measuring the instantaneous level of the received signal. The control circuit reduces the filter's cutoff frequency when the signal level falls and consists of a transistor acting as a variable resistor in the filter's resonant circuit.</p> |
