| 摘要 |
PURPOSE:To obtain automatic scan signal, by using the output at the two terminals which indicating the amplitude of the frequency shift and direction of the tuning meter drive circuit. CONSTITUTION:The automatic search output of the tuner A is fed to the FM intermediate frequency amplifying circuit FMIF and the detection circuit B. FMIF and the detection circuit B provided two output terminals 2, 3 as the tuning meter drive circuit and the muting output terminal 4. Positive ad negative voltages in proportion to the shift of frequency appeared at the terminals 2 and 3 and they are fed to the DC amplifiers C1, C2 in inverting and non-inverting states. High (low) and low (high) signals appear at the output terminals 7, 8 of the de-tuning discrimination circuit D depending respectively on the shift of frequency. The automatic scanning stop and tuning discrimination circuit F take the logical sum of the outputs of the terminals 7 and 8, and the output without de-tuning is given to the tuner A as the automatic scanning signal of the tuner A. |
