The 85W MagSafe 2 Power Adapter features a magnetic DC connector so if someone should trip over it, the cord disconnects harmlessly and your MacBook Pro stays put safely. It also helps prevent fraying or weakening of the cables over time. In addition, the magnetic DC helps guide the plug into the system for a quick and secure connection. When the connection is secure, an LED located at the head of the DC connector lights up; an amber light lets you know that your notebook is charging, while a green light tells you that you have a full charge. An AC cord is provided with the adapter for maximum cord length, while the AC wall adapter (also provided) gives you an even easier and more compact way to travel. designs to be the perfect traveling companion, the adapter has a clever design which allows the DC cable to be wound neatly around itself for easy cable storage. This power adapter recharges the lithium polymer battery while the system is off, on, or in sleep mode. It also powers the system if you choose to operate without a battery.