This 1975 tachometer for cars with platinum can serve as an idea for new projects. The components are from the era and a modern equivalent operational amplifier can be used.
Found in a 90s Popular Electronics, this sensor operates by infrared reflection. The components are...
This circuit, which can act as a shield, was found in a 1990 PE Hobbyst Handbook. The circuit...
This circuit was found in an old American manual. It is intended for testing SCRs and thermistors using...