This circuit was found in a 1964 Electronic Design. The circuit makes use of transistors of the time. Current equivalent transistors may be experienced.
This circuit was discovered in an English publication in 1979. The circuit can still be assembled with...
Found in a radio amateur magazine of the 1980s, this circuit uses components that can still be...
This circuit was found in the Philips integrated circuits manual of 1990. The integrated circuit must...