A Trisil is an electronic component designed to protect electronic circuits against overvoltage. Unlike a Transil it acts as a crowbar device, switching on when the voltage on it exceeds its breakover voltage. Overview A Trisil is bipolar, behaving the same way in both directions. It is principally a voltage-controlled triac without gate. The behavior of a trisil is similar to a diac, but unlike diac, trisil devices are commonly used to protect circuits from overvoltage. They act faster and ca… (More on Trisil)