As of February 9, 2007, suppliers of UL Listed transient voltage surge suppressors (TVSSs) must comply with the latest revisions of UL 1449 - Standard for Transient Voltage Surge Suppressors, 2nd Edition, to maintain their UL Listing. This white paper provides an overview of MOV-based TVSS failure modes,a review of the latest tests required by the UL 1449 standards and an overview of protection options.