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.
This circuit is a driver for R-2R network of AD converters. We found it in manufacturer...
This circuit was found in an American publication from the 60's. The transistor is made of...
This circuit produces an audio tone on the speaker or magnetic capsule. Rx must be such that added...