Found in an old Popular Electronics this circuit appears in other variations on this site and in this section. It uses a 7-segment common anode LED display as an indicator.
Found in a 1960 General Electric documentation, this crowbar circuit blows the fuse in case of...
This circuit was originally designed for testing crystals used in color televisions, but it works...
This bridge-biased transistor test circuit measures gain in the range 0 to 300. Circuit is from...