[TeMPOraL]

It should be obvious to just about anyone who was born in the last 100 years[0], as they should be all familiar with the basic principles of electrical devices: you power a device by connecting it with an outlet using a wire[1]. The underlying concept here is that a wire can transfer something useful from one point to another. Like electricity. Or, in this case, a voice signal.

Even if you found someone who's confused by the use of wire in this device, I think a 30 second explanation and demonstration would clear it up forever.

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[0] - Excepting the Sentinelese, and some other remaining groups with zero exposure to industrial-era technology - of which there's very few remaining on the planet.

[1] - And even in case of people who have never seen electrical devices, you can easily come up with a simple analogies to transfer this concept across all advancement levels. Voice traveling along a taut wire. Water flowing down the gutter. Grain rolling down a chute. Water dripping through, or flowing along, a soaked string. A bolas. Poking a bear with a stick. Etc.