Researched
Telephone
Bell’s telephone carries the human voice as an electric current: telephone networks eventually connect the world.
Open in the interactive tree →Alexander Graham Bell received the US patent in March 1876 (in competition with Elisha Gray; Philipp Reis had built a precursor device in 1861). The first exchange appeared in 1878, and over the 20th century it grew into the largest technical system in the world. The telephone lines later also carried the first internet connections.
Prerequisites
- Electromagnetism1831-1865Bell's telephone worked by electromagnetic induction
- Electric Telegraph1844
Unlocks
- Sound Recording1877
- Programmable Computer1941Zuse's Z3 was built from telephone relays
- Information Theory1948
- The Internet1969
- Optical Fiber1970