Using a 27-inch iMac (Late 2009 or Mid 2010) as an external display

With Target Display mode, you can use your iMac (27-inch, Mid 2010) or iMac (27-inch, Late 2009) with Mac OS X as an external display. Connect any computer or other device with a Mini DisplayPort to your 27-inch iMac using a Mini DisplayPort to Mini DisplayPort cable or using a converter that converts other electrical, video, and audio protocols from another source device to Mini DisplayPort compliant signals.  (Cables and converters available separately.)