We found this circuit in a documentation for radio amateurs from the 70s. The transistors can be the BC548. With it, small speakers of 4 or 8 ohms can be used as microphones.
This old circuit from a documentation from the 70s disconnects a TV from a signal obtained on the...
This traditional complementary symmetry circuit provides 20 W of rms power at a load of 8 ohms...
Using a CA3130 and a power transistor, this circuit can deliver a current of up to 500 mA with the...