As mentioned previously, the TMOV® and iTMOV® devices are made up of a Metal Oxide Varistor with an integrated thermally-active element. The device will automatically open-circuit when overheating occurs due to limited current abnormal sustained over-voltages. The integrated thermal activation element means it will not flame, fragment, or scorch when subjected to an abnormal over-voltage condition. Standard MOV’s are susceptible to thermal events. All ratings in the TMOV14 and TMOV20 devices are approved to UL1449 3rd edition.