Using an LDR as a sensor and an operational amplifier this circuit was found in the Encyclopedia of Electronic Circuits volume 5 from 1995. The circuit triggers an optodiac.
This transmitter was found in a 1993 documentation, but it can be assembled with operators like...
This transistor tester was found in a 1980 publication. The transistor can be the BC548 and the...
This circuit is from an Electronics Now from the 90s. The circuit uses a power integrated circuit...