Configuration (audio)
Radio were quite popular in flat land, do to the limited vision of their world tv wouldn't be as efficient, so most of there daily activities were done using sound from: shows, music, even video games, let's just say they didn't think about creating TV until a couple millenia later.
The radio was great for efficient identification. That way, they didn't need to constantly touch each other and risk harm. Eventually, they would evolve to become smaller and more portable for daily usage. The radio player you see the dimond using is one for identifying different individuals. They would put the slim disk in the box, and through the microphone, you would hear the configuration of the individual.








