This circuit for very long-time intervals was found in the March 1993 Radio Electronics magazine. Times of several days or even weeks can be achieved depending on the value of C1.
Found in a 1979 documentation, this circuit measures resistances on 5 linear scales. The precision is...
This circuit, from 1990 documentation, can be assembled with BC558 transistors for Q1 and Q2,...
Found in American documentation from the 90's, this JFET stage has an input impedance of 500 M...