The 85W MagSafe 2 Power Adapter features a magnetic DC connector so if someone trips over it the lead 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.&lt;br /&gt;&lt;br /&gt;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 full charge. An AC lead is provided with the adapter for maximum lead length while the AC wall adapter (also provided) gives you an even easier and more compact way to travel.&lt;br /&gt;&lt;br /&gt;Designed to be the perfect travelling companion the adapter has a clever design that allows the DC cable to be wound neatly around itself for easy cable storage.&lt;br /&gt;&lt;br /&gt;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.