Found in old documentation, this circuit can use modern equivalent components. The signal has good strength thanks to the use of a power transistor. The Q1 transistor is a unijunction of the time.
This circuit was found in Electronics Now. With it the dialing signals of a telephone are...
This circuit switches the brightness of the LED. We found it in an English documentation....
This circuit already explored in several diagrams in this section was found in a 90’s Popular...