Triode for Alternating Current (TRIAC) is an electronic component-of the thyristor family- that can conduct current in either direction when it is triggered. Due to this capability a TRIAC is also known as bidirectional triode thyristor or bilateral triode thyristor. TRIAC has 3-terminals. There are two Main Terminals, A1 and A2 which carry the heavy current that is being switched, and a control terminal, the Gate, G, which accepts the control signal to turn the switch on.