This 1969 circuit uses a 117 V filament tube powered directly by the power grid. The original circuit makes use of a charcoal microphone, a common component at the time.
September 2016 - Mouser Electgronics already has in stock the new moisture digital sensor HDC1010...
The frequency in this circuit is adjusted by P1 and given by C1. Short pulses, as the ones...
This booster circuit for audio signals, which is nothing more than an audio preamplifier for...