We found this touch control on a Popular Electronics from 1970. The circuit makes use of an integrated of the time. It can be adapted to use modern equivalent components.
The power supply shown in the figure provides voltages between 0 and approximately 15 volts, with...
Another triggered oscillator that we found in the November 1984 Radio Electronics magazine. The...
Found in a 1980s German publication, this circuit tests batteries by type. The circuit is based on a...