This simple circuit is powered by the logic circuit itself. Components are still common, although they were obtained from somewhat old documentation.
The transistors in this circuit are 2N2222 and general-purpose diodes 1N4148. The circuit is from...
We found this circuit in a 2002 documentation. The frequency of each note is determined by the...
We found this circuit in an Electronics Now from the 1990s. The circuit crashes when light strikes the...