This circuit, with 1 A output, was found in a 1975 documentation. The transistors admit equivalents and the transformer has windings according to the voltages being worked.
This circuit using an operational amplifier was found in old American documentation. It can be...
If the circuit oscillates, emitting sound, it is because the transistor is good. This simple...
Like the previous circuit, this is used in the analog part of the telephone lines. The same...