This circuit makes use of an optical coupler to isolate the telephone line. The circuit is from 1970s documentation. The components admit equivalents.
I found this circuit in an English magazine from July 1982. The circuit is still viable because all...
This 75 W power supply was found in American documentation from the 1980s. Transistors can be...
This simple transistor amplifier is from 1982 documentation. The output transistor must be mounted on...