This traditional circuit generates a 200 Hz sinusoidal signal. The frequency depends on the capacitors and the transistor can be a BC548. We found this circuit in a 1979 documentation.
Used with telephones at the time, this circuit was found in Popular Electronics from the 90s. The...
Found in a 1965 CQ magazine, this circuit uses period components. The unijunction transistor can...
This dimmer configuration is quite old, as it was found in a 1967 publication. The triac can be of...