This well-designed bistable configuration is for educational purposes. We found it in the September 19873 Radio Electronics magazine. The transistors are types from that time.
We found this receiver circuit for modulated light in a 90s Popular Electronics. Equivalent audio...
This field strength meter circuit was found in the March 1968 Radio Electronics magazine. The...
I found this circuit in a 1998 publication, but as all components are common, it can be easily...