The circuit is from an Electronics Hobbyst Handbook from the 90s, being valid for panels of the time, with lower performance. The circuit supplies 2.4V with 125mA current.
This circuit from the 40's is a conventional analog multimeter with several scales. Its accuracy will...
With this circuit, an external circuit can be controlled by turning it on or off and reversing it (if...
This circuit appears elsewhere on this site, but from different sources. Using the LM3900, we find this...