Using the 741 this basic circuit was found in the November 1973 Radio Electronics magazine. The power supply must be symmetrical. The components can be recalculated for other frequencies.
This circuit is from Popular Electronics from the 90's. The circuit discharges the battery with a...
We found this time base circuit in a timer project from the August 1972 Radio Electronics...
This sonic switch, vox or sonic relay uses a Darlington of the time that has a gain of 10,000. The...