We found this alarm circuit in a Radio Electronics magazine from July 1990. The power transistor must be equipped with a heat sink.
This small FM spy transmitter uses three transistors with an RF amplification stage. We found it...
This Audio System circuit was found in 1965 documentation. It is a 50 ohm line circuit with 22 dB...
This filter was found in an 80's English publication. However, it can be implemented with modern...