This circuit is from documentation from 1965. However, it can be created with modern transistors. Power comes from two 9 V batteries.
This 9 V battery eliminator was found in Radio Electronics magazine from June 1966. The transistor is of...
Using the ZN1034E which reaches 19 days interval, this is a simpler circuit which can be...
This analog meter circuit was found in the September 1989 issue of Radio Electronics magazine. The source...