This 9 V battery eliminator was found in Radio Electronics magazine from June 1966. The transistor is of medium power and must be equipped with a small heat sink.
This filter for the 300 Hz to 3 kHz range was found in an American documentation from the 90's....
This receiver is from a 1967 Japanese publication. The transistors are germanium and the output...
This simple electroscope with bipolar transistors is not the most sensitive, but can detect static...