The telephone and answering machines

The next idea to explore was finding a way to transmit sound to far distances. Alexander Graham Bell laid out the underlying technology for electromagnetic telephones and was granted a patent in 1876 for his improvements in telegraphy.

This introduced a new problem: what if you were not available if someone tried to call you? At the turn of the 20th century, Danish inventor Valdemar Poulsen invented the telegraphone, a device for recording and playing back the magnetic fields produced by sound.