what would they have thought 100 years ago?

Two young boys standing on a station platform. One of the boys is holding a slim rectangular object the size of a playing card, that he keeps on tapping with the tips of his fingers. There's a wire coming out of it, which splits into two in its middle. One of the ends disappears into the right ear of one of the boys. The other vanishes into the second boy's left ear. Both boys are moving their head rhythmically to and fro.