The circuit below is suggested by National Semiconductor in technical documentation on the LM3909. The circuit is powered by a single battery and has a very low consumption.
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. ...