A telephone is a device for transmitting voice over distances. It converts sound into electrical signals and back again. Alexander Graham Bell patented the first practical telephone in 1876. It changed how people communicated. It shrunk the world. It is still with us, though the form has changed.

Traditional telephones use the public switched telephone network. They are circuit-switched. A dedicated path opens for each call. Modern phones are mobile or VoIP. They use packet switching. The voice is digitized and sent as data. The telephone is no longer just a phone. It is a computer.

Telephone types

• Landline: wired, circuit-switched
• Mobile: cellular, wireless
• VoIP: internet-based
• Cordless: base station and handset
• Smartphone: apps and data

The telephone changed society. It enabled long-distance relationships. It made business faster. It connected emergency services. It evolved from a wall-mounted box to a pocket-sized computer. The telephone is one of the most important inventions in history.