| 摘要 |
PURPOSE:To improve the working of a squelch circuit and to obtain a receiving band device which can follow the speech quality for a noise detecting system of an FM receiver or a PM receiver, by detecting the noise level within a receiving band with no effect given from voices. CONSTITUTION:When the noises given from a discriminator 21 increase, the noise components of band pass filter circuits 1, 2 and 3 also increase evenly. The all inputs and then outputs of an AND circuit 16 are set at ''1''. When an auido signal is added with no change of the noise component, the frequency component of the audio signal exists at random within a band. Therefore the circuits 1-3 are never set at a working level at one time. As a result, the inputs of the circuit 16 are not set at ''1'' at one time, and the output of the circuit 16 is set at ''0''. Thus it is possible with such a circuit to detect the noise components within a receiving band without receiving any effect of the auido signal. |
