... for Armature: Zinc;Signal output: Dry contact, max rating of contact current 3AAdvantage:Easy to install, no frame door ... two years,maintenance forever, change within 3 months because of product quality itselfFinishes for Shell: Anodized aluminum & surface ... for Armature: Zinc;Signal output: Dry contact, max rating of contact current 3AAdvantage:Lower power consumption, hight efficiency;Suitable for ...