Optical potentiometer (CB22159E)

This voltage-controlled potentiometer using an LDR was found in an English documentation. LDR is common and LED of any type.

Signal injector (CB21554E)
The CK722 transistor used in this circuit is one of the first commercial types in the world. The...
Automatic Dimmer (CB18864E)
This automatic dimmer for incandescent lamps was found in a European publication from the 1980s. The...
Voltage doubler with 555 (CB1230E)
This traditional doubler configuration with the 555 can be found in other articles on the author’s site....