The selected circuit was found in GE's 1977 semiconductor manual. 3N84 is a controlled silicon switch and SCRs support equivalents. The transistor can be a BC558, depending on the supply voltage.
This small regulator was found in a Motorola 1968’s documentation. It is a current regulator using...
This circuit was found in a 1968 US publication. Transistors used are uncommon today. The circuit...
This electronic bait, or fish attractor, produces a sound in the water that attracts fish of...