This circuit is from an ancient American documentation. The integrated circuit is 741 and the power supply must be symmetrical. The passing band is centered at 1 kHz.
I found this circuit in a Popular Electronics from November 1999. The magazine is no longer...
This interesting circuit, found in an old American publication, measures alternating signals in a...
This is the well-known lightning lamp that was published in the March 1988 issue of Saber...