This circuit is from a 1970 General Electric documentation. It can be found with variations on this website. The components used are common today.
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....