This circuit comes from a Gernsback Publications of the 90s. The circuit uses a general-purpose transistor as a sensor. The power supply must be symmetrical.
This high-gain circuit was found in an American publication from the 1990s. The circuit can use...
This circuit automatically controls the degree of illumination. As the circuit is from 2001, it...
This circuit was found in a Radio Electronics from April 1990. The circuit has 5 equalization...