This circuit was obtained from an old American documentation, and practically any general-purpose transistor and sensitive relay can be used according to the supply voltage.
In this phase shift circuit, the transistor can be any general-purpose transistor. The circuit is from...
This 2004 circuit is based on the ionization effect that occurs in old incandescent lamps with...
This circuit is from Delco Radio found in a 1968’s documentation. The transistors are of the time...