The integrated circuit used in this 2002 project is not very common. It is powered directly by the telephone line, requiring no power supply.
This project was found in a 1981 documentation. It consists of an interesting audio oscillator that...
This circuit, which can only be used with incandescent lamps, is adapted to the common wall...
This simple transistor gain test acts as an oscillator for the transistor under test. The circuit is...