Person A speaks, and their words appear, in their own language, on the screen like a chat bubble. On the other side of the screen, the query is translated and printed in Person B's language. Rinse and repeat, and in this manner business can be conducted.
Additionally, the screen can be used as signage when not in conversational use:
Japan's Seibu Railway has installed one of the windows at the information desk at the Seibu-Shinjuku station in Tokyo. Here's the window in action:
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