| 摘要 |
PURPOSE:To simplify an operation for channel selection at a weak field input signal level of an inferior S/N, by giving automatic tuning only to the FM stereo broadcast with an automatic operation of channel selection and therefore eliminating confirmation for the stereo broadcast when the tuning is obtained. CONSTITUTION:FM stereo-monaural changeover switches 11-1 and 11-2 are provided to a radio receiver which is capable of an automatic operation of channel selection. Then a controller 10 is connected to the switch 11-1 via a 3-input AND circuit 9, and at the same time an FM demodulator 5 is connected to the switch 11-2. The DC signals 901 and 902 supplied from a DC amplification/switch circuit 6 and a detecting circuit 7 are fed to the circuit 9. At the same time, a stereo discriminating signal detecting circuit 8 is connected between the side of a contact (a) of the switch 11-1 and the demodulator 5. Then a normal tuning point is detected by the levels of the input signal and discriminating signal supplied from the circuit 8 and the tuning voltage of an FM wave detector 4 and under the control of the controller 10 when the switches 11-1 and 11-2 are set in the stereo mode. Then the automatic channel selecting operation is discontinued. |
