Modern emergency telephone powered by sound alone.
The network that connects most phones together is known as the PSTN (public switched telephone network).
Fixed phone lines are usually copper wirelines which form a circuit between the subscriber and the exchange, although some recent installations may use optical fiber for part of the distance. [...]

The telephone or phone is a telecommunications device designed to transmit speech by means of electric signals. It was invented around 1860 by Antonio Meucci who called it teletrophone. The first recorded public demonstration of Meucci’s invention took place in 1860, and had a description of it published in New [...]