Mobile phones are radio telephones in which calls are routed through a network of radio aerials, or masts, linked to the main public telephone network. (Landline phones, which carry calls along electrical cables, work in a completely different way.) A mobile phone sends and receives calls without any wire connections. Instead, it uses electromagnetic waves to send and receive the sounds that would normally travel down wires. The first hand-held mobile phone call was made in 1973, using a handset that weighed about a kilogram (more than two pounds).

Digital signal

When you speak into a mobile phone, a tiny microphone in the handset converts the sounds of your voice into a pattern of electrical signals. A microchip inside the phone digitizes them (turns them into strings of numbers). The digital signal is carried by a radio wave and beamed out from the phone's aerial. The radio wave travels at the speed of light until it reaches the nearest radio aerial.

Mobile phones use radio waves for making calls or sending messages. The signals do not go directly from one phone to another. Instead, they are picked up by a transmitter in your local area, or “cell”. They are then passed along the network to a phone in another cell, or to a landline phone.

In a cellular telephone network, each cell (part of the landscape) has a radio aerial that communicates with any mobile phone that moves into it. The most-used digital network is GSM (Global System for Mobile communication).

Fifth generation (5G) phones came into use in 2019. To begin with, speeds range from 50 mbps to more than 2 gbps, but these are expected to rise to 100 gbps—a hundred times faster than 4G. In addition to simply providing faster speeds, 5G networks will also need to meet the needs of new technologies, such as the Internet of things (IoT). This is a system of inter-connected devices (including smartphones) and appliances, such as lighting, thermostats, home security systems and cameras, together forming what is called the "smart home".

Smartphones

The most recent mobile phones are known as smartphones. They are mini-computers: they can be used for email, browsing the internet, taking digital photos and video, maps and satnav, using apps and playing music and games. Smartphones can send and receive information much faster than older phones. They include touchscreens and web browsers. With 3G, 4G or 5G digital technology, it means they can be used to send and receive computerized data, including text (SMS) messages, web pages, MP3 music files and digital photos.