A Triac is a high-speed solid-state device that can switch and control AC power in both directions of a sinusoidal waveform
4 possible triggering modes of operation Ι + Mode = MT 2 current positive (+ ve ), Gate current positive (+ ve ) Ι – Mode = MT 2 current positive (+ ve ), Gate current negative (- ve ) ΙΙΙ + Mode = MT 2 current negative (- ve ), Gate current positive (+ ve ) ΙΙΙ – Mode = MT 2 current negative (- ve ), Gate current negative (- ve )