This circuit that appears in several versions in this section and on this website was found in documentation from the 1980s. The transistors can be of any general purpose NPN type like the BC548.
This circuit prevents the accidental inversion of the input polarity of a source to cause damage to...
Found in a Radio Electronics magazine from September 1958, this circuit has an LDR powered by the...
This circuit was found in General Electric documentation from the 1980s. The circuit is intended...