This control circuit using a low voltage switch was found in the September 1987 Radio Electronics magazine. The triac must be matched to the load and the mains voltage.
This stethoscope or hearing aid amplifier has excellent gain. It was found in Popular Electronics from...
Found in Fairchild documentation from the 90s, this circuit generates signals with the...
This configuration, widely used in our articles and on this website, uses a 555 to control a relay...