We found this circuit in a documentation for radio amateurs from the 70s. The transistors can be the BC548. With it, small speakers of 4 or 8 ohms can be used as microphones.
A touch in this circuit turns-on the lamp or the relay. Power supply is according the lamp or...
This an old commercial receiver found in a year 1958 magazine. The circuit uses some transformer...
We found this very simple cable fitting circuit in an Electronics Now from the 90s. ...