The device that carried the human voice over a wire — replacing coded signals handled by trained operators with direct conversation between ordinary people, and building the largest machine ever assembled to do it: the network.
The telegraph sent dots and dashes. A trained operator decoded them at the other end. The telephone sent the voice itself — your voice, to someone you knew, in real time, across any distance. That shift, from coded message to live conversation, required not just a new device but an entirely new kind of network, and that network became the largest machine human beings had ever built.