Audible and visual signals. Signal differentiates between voltage and metal. Uses 9 volt battery (not included). Can find power and lighting cables in walls, rebar and pipes in concrete, conduit and cables in ceilings. ///brand_for_product_detail=Zircon,close_out=Yes,companydescription=Zircon - Made in Hong Kong,condition=New,condition_google=new,cost=2.000000,countrymade=Made in Hong Kong,country_flag=no_selection,featured=0,flag=no_selection,identifier_exists=0,instock=in stock,is_recurring=0,listprice=4.50,madeby=No,madeinusa=1,manufacture_country=Imported / Other,product_image_size=Default,product_page_type=Default,sellprice=9,shopping_ad_bestseller=No,smart_campaign_bestsellers=Rest of Smart Campaign Products,square_product_image=https://square-production.s3.amazonaws.com/files/8e71fa8d2bfea99dedb59083ac0b1f5d160a20df/original.jpeg,store_price=9.000000,sw_featured=No,url_path=zircon-voltage-metal-electronic-sensor