Usually already the circuit F.M. Discriminator the majority will give output that can modify tall and lower 0V depend on something tuning and often use drive Tuning meter at have junction universal position.
This circuit designs by use LED 3 pcs. Replace which regard as suit very with the usability. By when institute off-tune output of Discriminator change go to tall more or lower 0V make LED1 or LED3 shine respectively. When output of Discriminator equal to 0V LED2 stick for inform that something tuning best effective both of transistor Q1 with Q3 that use circuit model silicon PNP small signal the multi-purpose and Q2 with Q4 be model silicon NPN small signal the multi-purpose.
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