This circuit indicates when a rain is acidic by monitoring its pH. The circuit is from a 90s RE Experimenter Handbook. Some components used can be difficult to obtain today.
This circuit can be used in decoration or to draw attention, in a “fake” assembly for example. What he...
This sophisticated alarm with traditional components was found in an ancient American...
We found this AM radio in a 1957 transistor application manual, published by Raytheon. The...