This tachometer and dwell meter for old cars was found in a 1975 documentation. The circuit is a reference for those who want to recover or maintain an old car.
This interesting passive circuit from an 80's publication measures the distortion of an audio...
Figure bellow shows how the flip-flops of a 4027 can be connected to perform a divide-by-5 counter [odd...
This analog meter circuit was found in the September 1989 issue of Radio Electronics magazine. The source...