Brief description
Holograms are used as telephones several times in the game, but one instance is extra prominent: Raynor and Valerian Mengsk are talking face-to-face when Valerian says "you might particularly enjoy this next step", pushes a button, and then a giant holographic head of Arcturus Mengsk appears. Raynor is clearly surprised by this. Arcturus asks Valerian to explain himself, seemingly unaware that Raynor is present. Valerian explains his plan to his father, and when Arcturus doubts him, Raynor jumps in, prompting a surprised response from Arcturus. (meaning that the hologram has a very limited field of vision in the room "we" are in)