Suggested by a 1968 Motorola power semiconductor manual, this circuit uses a special transformer and transistors from the era. The frequency is 60 Hz.
The circuit shown, found in a 2004 documentation, allows the use of a telephone, without the...
Here is a very useful circuit that can be expanded, including the use of more integrated circuits...
This circuit was obtained in a 1973s documentation. The transistors may be BC558 for the PNP and...