This circuit was found in a Popular Electronics from the 90s. It is intended to power the filament of old radio valves in recovery works. It is indicated for tubes that use 5 V of filament.
This alarm does not interrupt its operation when the power is cut. A battery is kept at a constant...
The sophisticated signal tracker/follower with a JFET and integrated circuit 741 was found in a...
This circuit, found in a publication from the 1970s, produces a 1 Hz sinusoidal signal....