Telecom atlas
How a phone call works, from the voice in the handset to the cable on the ocean floor, and how each part came to be. Each subject is a working machine you can explore, with every fact written out beside it.
Across the planet
How a call crosses the ocean
A submarine cable, or undersea cable, is a cable laid on the seabed between coasts. Almost all the calls and data that cross an ocean travel through one.
ExploreAcross the planet
The cables, the light and the numbers that carry a call around the world.
Optical fibre How light carries your call through glass Optical fibre carries your call as flashes of light through a strand of glass thinner than a hair: light for a one, dark for a zero. Coming next
- How a number finds one phone among billions
- How a call passes from one operator to another
Across the city
How a call travels between buildings, over the internet and into the phone network.
Coming next
- How a call travels over the internet in small packets
- How a call is set up before anyone speaks
- How the voice travels once the call is set up
- How an office connects to the public phone network
- Why delay makes a call feel wrong
- How data finds its way across the internet
Inside the building
The office: its phone system, its router, and the rules that pick who answers.
Call routing How a call finds the right person Call routing is the set of rules that decides which phone rings when you call a company. Coming next
- How an office phone system connects calls
- The same phone system, moved into a data centre
- How the office router lets calls in and out
- One number on the desk phone and the mobile
Inside the device
What happens inside the phone in your hand or on your desk.
Telephone How a phone turns your voice into electricity A telephone turns your voice into an electric current that rises and falls with it, sends the current along a wire, and turns it back into sound at the other end. Coming next
- What sits inside an office desk phone
- How your voice becomes numbers, 8,000 times a second
On your mobile
How the phone in your pocket finds the network, at home and abroad.
Coming next
- How a call reaches your mobile
- How a SIM proves who you are to the network
- How a mobile call becomes an internet call over 4G
- How your mobile calls over Wi-Fi
- How your phone works in another country
History
How calls worked before, and why the old network is closing.
Coming next
- How operators connected calls by hand
- How machines replaced the operators
- Why the old copper network is closing now
- From 1876 to the cloud
Today
What is changing about phone calls right now.
Coming next
- How callers fake the number you see
- How an AI answers a call