The transistors of this circuit found in an English 1980s documentation may be the modern BC548 equivalents. The circuit is battery powered and the earphone must be crystal.
This radio's transistor is powered with the signal's own energy, producing its amplification....
Found in a 90s Electronic Design, this circuit can be used as a shield in current projects. The...
The integrated circuit used in this regulator is not very common today. The circuit is from old...