This circuit uses an LED (called SSL) to regulate current in a configuration with complementary transistors. The circuit is from 1970 General Electric documentation.
This ohmmeter can be made with a scrap milliammeter used for continuity tests or even resistance...
This circuit was found in the November 1992 issue of Radio Electronics magazine. The circuit has...
Found in an English Maplin documentation from 1983, this circuit generates separate frequency...