This 1969 circuit uses a 117 V filament tube powered directly by the power grid. The original circuit makes use of a charcoal microphone, a common component at the time.
This was the original title given by the publication of the 80s in which we found it. Similar...
This circuit for analog video signals was found in a 90s 303 Circuits. The used digital switch is...
This circuit mimics the trill of a bird. We found it in an American documentation from the 90s. It is...