I'm excited that we finally have a public videophone at Yosemite. It's at Yosemite Lodge. Just go to the front desk and ask for the remote and key. When the clerk gives them to you, walk down the hallway to the right of the front desk; the videophone is at the end. It's available all day and all night. You can make outgoing calls, but the videophone does not accept incoming calls.
In 2012, Yosemite had a public videophone installed at Yosemite Valley Lodge. Watch this video to learn how and where to access it. (No audio, but transcript available.)