The purpose of this circuit is only to increase the input resistance of a multimeter, since there is no voltage gain. The batteries are 9 V and operational equivalents can be used.
This circuit is from a 1965 General Electric Hobby manual. The circuit uses only passive...
We found this circuit in a 1967 RCA SCR manual. The circuit uses components from the era. The...
Found in American documentation from the 1970s, this circuit can be designed based on a modern SCR,...