Found in a 1980s manufacturer documentation, this circuit can be used as an optical shield. The integrated circuit is from the era and modern equivalents can be tried out.
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...