This circuit also detects IR, providing LED indication. The circuit is used to indicate humidity in bench tests. We found it in the Radio Electronics magazine of February 1990.
This circuit was found in the magazine of radio amateurs 73 in a 90's edition. The components are...
Equivalent transistors like the BC548 can be used on this 1969 Mullard circuit. The circuit has two...
This alarm circuit triggers when S1 opens. The circuit from a January 1975 Radio Electronics...