Can a voice be carried on a wire?

That time, that place

The telegraph already spanned continents, but it sends only dots and dashes — on and off. A person encodes, another decodes.

A voice cannot go that way. A voice is a continuous, constantly varying wave.

Why this question

Bell taught deaf students. His mother and his wife had both lost their hearing, and he worked with sound and speech all his life.

His idea: sound is air trembling. Let that trembling shake a thin membrane, and let the membrane's motion continuously vary the strength of a current. At the far end, use that current to shake another membrane.

Not on and off, but a current whose strength keeps changing.

What was found

In March 1876 the first sentence, to an assistant in the next room, is on record: a request to come here.

On the same day another man filed for a similar device — Elisha Gray, hours apart — and litigation ran for decades. There are claims that Antonio Meucci was earlier still.

What matters is that the character of communication changed: from something requiring a trained operator in the middle to something anyone could pick up and speak into. And this company's laboratory would build the transistor seventy years later.