Indicated for stereophonic sound applications, this circuit was found in the April 1983 issue of Radio Electronics magazine. The indicated circuit is the NE570, launched at the time.
For those who like experimental circuits, here is a sequential flasher system with LEDs, which can be...
This circuit was found in an ancient American documentation. The integrated circuit is of the time...
This circuit was found in a 1977 Radio Shack documentation. The circuit is tuned to 1.4 kHz, but...