This variable filter that lets frequencies from 500 Hz to 1500 Hz pass through was found in a Popular Electronics from the 90's. The operational amplifiers are the 741.
This simple circuit, based on an astounding 555, was found in a 2001 documentation. The circuit...
This circuit generates sinusoidal signals that depend on the input oscillator. The circuit is from...
This is one of many power control or dimmer configurations that we have found on this site and in...