This circuit was obtained from a 1947 amplifier manual. The circuit makes use of a transformer source, but it can also be battery powered.
We found this circuit from a commercial megaphone in a Japanese publication in 1967. The circuit is...
This circuit was found in an Elektor from the 90s. The circuit is critical, requiring a very...
This circuit was found in a 1987 documentation but uses components quite common in the current...