This CMOS circuit was found in a Popular Electronics from the 80's. The circuit consists of a counter that has its output activated when the selected key combination is pressed.
The operational Amplifier used in this circuit is uncommon today. However, the same circuit can be...
This small blocking oscillator for approximately 1000 Hz was found in an American documentation from the...
We found this circuit in a Radio & Electronics Constructor from November 1975. The magazine no longer...