In this circuit the triac conducts when switch S1 is opened. We found it in the October 1987 Radio Electronics magazine. The triac is controlled according to the load.
In the figure we have a bistable multivibrator using an operational one. The circuit is from old...
This is another of the Star Trek red alert circuit that you can find on this site. We took this...
This circuit for testing zener diodes by lifting their curve on an oscilloscope was presented in...