We found this precision circuit in a manual from the 80's. The operational amplifier is of a common type at the time, and equivalents can be tested. Transistors are general purpose types.
This well-designed bistable configuration is for educational purposes. We found it in the...
We found this circuit in the January 1988 issue of Radio Electronics magazine. The circuit can be...
This crystal or galena radio is one of the many versions available on this website. This is from a...