On this day in 1878, Alexander Graham Bell patented the first telephone.

We’ve been talking a lot about milestones in communications history lately, including Thomas Edison’s invention of the telegraph and the phonograph. At this time of rapid development, Alexander Graham Bell was working on finding a way to transmit speech by wire.

The first telephone used a thin iron plate (called the diaphragm), which vibrated in response to sound waves. The rhythm was then sent magnetically to a wire, which connected to another iron plate. The instrument on the receiving end could then replicate the sound.

Bell contested Thomas Edison’s Western Union Telegraph Company for the development of similar telephone technology, eventually resulting in Bell gaining a foothold in the industry with his company, which was later called AT&T.