| 摘要 |
PURPOSE:To eliminate the switch operation with every tuning action and thus simplify the operation for an FM radio receiver or the like, by securing an automatic on/off control for the AFC action in accordance with the intensity of the received signal. CONSTITUTION:No output is delivered from the intermediate frequency amplifying circuit in case when a receiver is under the detuning state. Accordingly, the output of the control circuit 8 is approximate to zero. In this case, the reference voltage applied to the input terminal (a) of one side in the switching circuit 7 emerges at the output terminal (d). This voltage is then applied to the variable capacity diode 6 forming the local oscillating circuit 3. Then the tuning action is started to get close to the tuning point, and thus the circuit 7 is switched. As a result, the AFC signal applied to the input terminal (b) is applied to the diode 6. |
