We found this circuit in a 1971 documentation. The circuit can be assembled with more modern transistors such as BC548 for Q1, BC558 for Q2 and BD135 for Q3.
This circuit is from a 1966 American documentation. The circuit uses a photo-FET, an unusual...
We found this circuit in a circuit manual from the 1980s. The circuit eliminates the conductive...
This circuit was found in a 2006 documentation. With it the telephone bell can be tested. When we...