We found this circuit in a Hands-On Electronics from the 90s. The circuit must be connected to an external amplifier. Frequency control is capacitive, using an antenna for this purpose
The CK722 transistor used in this circuit is one of the first commercial types in the world. The...
This automatic dimmer for incandescent lamps was found in a European publication from the 1980s. The...
This traditional doubler configuration with the 555 can be found in other articles on the author’s site....