TRIAC, from
triode for alternating current, is a
generic trademark for a three terminal
electronic component that conducts
current in either direction when triggered. Its formal name is
bidirectional triode thyristor or
bilateral triode thyristor. A thyristor is analogous to a
relay in that a small voltage and current can control a much larger voltage and current. The illustration on the right shows the circuit symbol for a TRIAC where A1 is Anode 1, A2 is Anode 2, and G is Gate. Anode 1 and Anode 2 are normally termed Main Terminal 1 (MT1) and Main Terminal 2 (MT2) respectively.