This circuit is from a Popular Electronics from the 90s. It uses an opto-coupler with SCR directly controlling a 20 mA current load.
This circuit generates signals of different waveforms thanks to the use of a relaxation...
This converter converts signals from the 50 MHz band to the AM band, making it possible to receive...
This circuit appears in various parts of this site and this section, with diverse origins. This is from...