Zio Bluetooth 4.1 Hands-Free Car Kit Bluetooth Audio Music Receiver Adapter with Built-in Mic/3.5mm Aux Cable/USB Charging Cable/3M Adhesive Base for Smartphones (Black) Built-in microphone,you can receive your calls with your hands free when your are driving.Bluetooth Hands-free Car kit help to answer and receive calls for your iPhone,BlackBerry, Samsung,etc. Help to listen to music wireless in your car and easily control.Next/Previous song,volume Up/Down.When you start your car,it will power on again and it can connect automatically. Important NoteThe power system in some kinds of car or vehicle contain noise interference from power earthing terminal,it will affect any Bluetooth receiver that supply power by the car power system , In such a situation, you need a Ground Loop Isolator (Please search ASIN B019FC6ZQQ on Amazon to get it ) connect to the AUX Jack in car to eliminate noise.You will enjoy good quality sound when use it with Ground Loop Noise isolator . Double-link:Support multi-point connection technology;Connect two phones Simultaneously.Automatically connect to the last connected phone. Working range will be 10meters (about 30 feet);It should be powered by USB port first.The car charger isnt included in the package,you can choose our Zio Car Charger or other chargers as you like.