This circuit was found I a 1965 Radio Schack documentation. The transistors are from that time, admitting equivalents. The transformer has 500 ohm primary and secondary depending on the speaker.
This control for 1200 W of power was found in the documentation of General Electric of 1966 has a...
I found this circuit in an old English magazine from 1979, but it can be easily assembled with...
This circuit imitates the singing of a bird intermittently with the intermittency determined by C1...