This circuit is from a 90s documentation. It has a hysteresis and uses a light sensing bridge. The circuit generates a 1000 Hz modulated 10 Hz signal. The signal must be applied to an amplifier.
An audio signal is applied to the input of this circuit. Depending on the position of the selector...
This circuit uses a dual floodgate MOSFET not very easy to obtain today. Its handling is very...
This crystal or galena radio uses a germanium diode. C1 is an old radio variable and L1 has 100...