This circuit was found in a 1968 US publication. Transistors used are uncommon today. The circuit can be adapted to operate with modern equivalent components.
This circuit was obtained from an English publication from the 70's. The circuit is still current for...
This circuit makes use of an unusual Analog Devices component today. The circuit is from a 90's...
This circuit was found in a 1974 documentation. The bipolar transistor can be the BC548 and at the...