All HDTV take 60Hz input and have 60Hz outputs. "120Hz" and "240Hz" refers to internal video processing done by the HDTV's electronics basically for smoother video playback and "improved" video quality.3D Capable HDTVs
are the exception. They are just like 120Hz PC monitors; they take dual 60Hz inputs (120Hz total) and outputs at 120Hz as well. This are the only exception. Here's an example of a 3D capable HDTV, the Samsung PN50C7000YF:http://www.samsung.com/us/video/tvs/PN50C7000YFXZA
Only the 7000 series and above are 3D HDTVs. The 6000 series and below are your typical HDTV with "120Hz" or "240Hz" video processing.