HT5404: About AirPlay Mirroring in OS XLearn about About AirPlay Mirroring in OS X
Currently Being ModeratedNov 3, 2012 9:44 AM (in response to paulPR)
You're talking about the "Mirroring" icon and not all machines that can run Mountain Lion support it. If it doesn't show up in the Menu bar more than likely your machine doesn't support mirroring your Display to the Apple TV.
Currently Being ModeratedNov 3, 2012 10:14 AM (in response to QuickTimeKirk)
Below you may find the guidelines and requirements for Airplay mirroring on OS X:
Hope that helps,