This circuit was found in a Popular Electronics from the 90s. The circuit has 4 frequency ranges selected according to the capacitors. Signal is rectangular.
The transistors of this old circuit from the 60s can be the BC548, in a current version. The...
This electronic soldering gun circuit was found in the December 1998 Electronics Now magazine. The article...
This circuit was found in an American documentation from the 90's. What it does is provide at the...