This circuit was found in an English publication from the 70s, an article that teaches how to calculate instruments. The circuit is still current and can be built with an analog indicator of 100 uA.
Found in a 90s Popular Electronics, this circuit triggers a load from the audio signal applied to...
This circuit generates alternating magnetic fields in a small electromagnet for various...
This dimmer, from an old publication, can use almost any triac and in shooting a neon lamp. The...