The UL Mark indicates that either Underwriters Laboratories or an equivalent nationally recognized testing laboratory (NRTL) has tested and determined that a product meets UL specified product safety requirements. This certification allows a manufacturer to show that their product is “UL Listed” by using the familiar UL logo. For power supplies, this mark would be applied to external units and DIN-Rail mount supplies, as well as most consumer electronics including computers. Where a supply is considered to be a component part it, along with other electrical components, may be marked with the reversed UR symbol indicating a “UL Recognized” certification.