| 摘要 |
PURPOSE:To respectively optimize the turning frequency and attenuation depending on the difference from a system in one sound trap by switching the trap turning frequency at the reception of each standard system and obtaining the required attenuation for the changeover of the circuit form. CONSTITUTION:In receiving the 1st standard system, a 0V voltage is generated from a discrimination circuit 9, a diode 4 is nonconductive and the capacitor 2 is not operated in terms of circuit. On the other hand, the voltage of 10V inverted by a polarity inverting circuit 8 is fed to the diode 7 and since the diode 7 is conducted and a trimmer capacitor 6 is connected in parallel with the sound trap 5. In adjusting the trimmer capacitor 6 so as to be turned to the frequency fs1, a serial/parallel resonance trap is constituted by a capacitor 3, a sound trap 5 and the trimmer capacitor 6 to attenuate the frequency fs1. In selecting the capacitor 3, the trap with comparatively small attenuation is realized and the selectivity characteristic shown in full lines is obtained. The processing above is similar in receiving the 2nd standard system.
|
