An interactive teardown
How a mobile phone
actually works
It is a radio, a camera, a computer and a battery, squeezed into seven millimetres of glass and aluminium. Below, seven things you can poke at: pull the phone apart layer by layer, follow your voice all the way to the other person's ear, walk between cell towers, and watch the screen feel your finger.
- ~0.2 Wwhat your phone radiates — less than a nightlight
- ~3 µsfor the radio wave to reach a tower 1 km away
- 120×/sthe screen asks its grid whether you are touching it
01
The stack, layer by layer
A phone is not a box of parts — it is a stack. Every layer is as thin as it can be so the ones above and below it fit. Tap a layer to pull it out.
Tap a slab, or use ↑ ↓ once one is selected.
02
Your voice, all the way there
Saying "hello" moves a diaphragm by a fraction of a micron. Twelve transformations later it moves someone else's eardrum, hundreds of kilometres away, about a tenth of a second later. Press play.
03
Why your phone carries so many radios
One number decides almost everything about a mobile network: the carrier frequency. Low frequencies travel far and pass through walls but carry little. High frequencies carry enormous amounts and stop at a window pane. Drag the slider.
04
Cells, and the moment you are handed over
The network is a mosaic. Your phone constantly measures every tower it can hear and reports back; when a neighbour has been convincingly better for long enough, the network moves your call mid-sentence. Drag the phone — or let it walk.
05
How the glass feels your finger
Under the glass is a grid of transparent electrodes. Where your finger comes close it steals a tiny amount of charge — femtofarads — from the crossing below it. The controller reads the whole grid, finds the bump, and hands the operating system a single pair of coordinates. Move your pointer over the panel.
Move over the panel · press and hold for a firmer press · touch works too
06
One chip, a dozen specialists
Almost everything is on a single piece of silicon the size of a fingernail. It is not one processor but a committee of them, and the trick is that most are asleep most of the time. Pick a workload and watch who wakes up.
07
From your tap to the transistor
A tap on a button crosses seven or eight layers of software before anything physical happens — and one of those layers runs on a processor your operating system cannot see. Click a layer.
The short version
It is a radio first
Everything else is decoration on top of a machine whose job is to turn bits into a modulated wave and back, thousands of times a second, while moving.
It is mostly asleep
The reason a phone lasts a day is that its blocks race to finish and then power down. Average draw is measured in tens of milliwatts, not watts.
The network does the hard part
Your phone is one end of a scheduled conversation. The tower decides, millisecond by millisecond, who transmits, when, on which subcarriers, and how densely.
Two computers, one box
The applications processor runs your OS. The baseband runs its own real-time OS, its own firmware, and its own timing — and the two only exchange messages.