This circuit is from a 1968 documentation. It makes use of thermistors (NTC) to indicate overheating of charged batteries. Modern equivalent components can be used.
Found in Popular Electronics from the 90s, this circuit uses a reed switch on the rails as a...
Using a CMOS 4001, this circuit provides frequency readings on an analog instrument. The idea of...
Used with infrared remotes at the time, this circuit was found in a 1991 RE Experimenter Handbook....