We found this circuit in a documentation from the 90's. Information on the A/D converter was not given but types can be used according to the application.
This circuit, which in our times would be called a shield, can also be used with other loads. The...
This circuit is from an old American documentation from the 70s. Transistor 2N3904 can be replaced by...
This application of the 555 was found in the November 1992 Radio Electronics magazine. The...