How does a TV station work?
A news channel is a factory that runs live, to the second. Read a teleprompter, cut between cameras in the control room, time a satellite hop, squeeze a billion bits a second, follow the signal to your dish and see how ratings meters decide who gets paid.
▶ Play with it · Read the 60-second explainer · Watch the 40-second video
- A stage built for the camera. A news studio is a desk, a backdrop and three or four cameras on wheeled pedestals, lit by key, fill and back lights from a grid. The anchor reads a mirrored script reflected in half-silvered glass over the lens, and green-screen corners swap every green pixel for a weather map.
- The control room picks every picture. In the gallery, a multiviewer shows every source at once. The vision mixer lines up the next shot on Preview and, on the director's call, cuts or mixes it to Programme. A red tally light shows which camera is live, and lower thirds and the logo are keyed on top.
- Why the reporter pauses. A live report bounced off a geostationary satellite travels over 72,000 km up and down: about a quarter of a second per hop. The question takes one hop and the answer another, plus encoding time. Bonded 4G/5G backpacks split the video over several networks, with about a second of buffer.
- A billion bits, squeezed. Uncompressed studio HD is about 1 billion bits a second. Codecs such as MPEG-2, H.264 and HEVC cut it to a few megabits by rounding away fine detail in 8×8 blocks and sending only motion and changes between I, P and B frames. A playout server then runs the channel to the second and logs every ad.
- Four roads to your home. The channel goes up to a satellite such as GSAT-15 and down to DTH dishes, whose LNB shifts the signal for the set-top box, and to cable headends that feed MSOs and local operators. Doordarshan towers and OTT streaming are the other roads. Ku band suits small dishes but fades in monsoon rain.
- Ratings and trust. Ad money follows BARC's ratings, measured by about 55,000 secret meter homes that hear hidden audio watermarks. Thin slices of a sample have big error bars, and bribed meters can skew them. News channels answer to the Programme Code and the NBDSA, and good newsrooms fact-check before they air.
| Term | Meaning |
|---|---|
| Teleprompter | A monitor and half-silvered glass in front of the lens that let a presenter read while looking at the camera. |
| Chroma key | Replacing every pixel of one colour, usually green, with another picture. |
| Vision mixer | The switcher that cuts and mixes between cameras and other sources, and the person who runs it. |
| Tally light | A red lamp on a camera that is live on air. |
| Geostationary satellite | A satellite 35,786 km above the equator that circles once a day and so seems to hang still. |
| Codec | A method for compressing and decompressing video, such as MPEG-2, H.264 or HEVC. |
| Playout | The system that plays a channel's programmes and ads to air on schedule and logs them. |
| LNB | The box at a dish's focus that amplifies the signal and shifts it to a lower frequency for the cable. |
| TRP | Television rating point: the share of viewers a programme gets, measured from a sample panel of homes. |
From an attic in London to a teleport in Noida: a century of putting live pictures on the air.
- 1926 · Live faces on a tiny screen (John Logie Baird, London)
- 1936 · The first regular TV service (BBC, Alexandra Palace, London)
- 1959 · India's first TV broadcast (All India Radio (later Doordarshan), Delhi)
- 1975 · Satellite TV for 2,400 villages (ISRO and NASA (SITE), Six states of India)
- 1982 · Colour, a national channel and the Asian Games (Doordarshan, New Delhi)
- 1991 · Star and Zee arrive by satellite (Star TV; Subhash Chandra (Zee TV), Hong Kong and Mumbai)
- 2004 · Free TV from a dish (Prasar Bharati, India)
- 2015 · BARC's meters start counting (Broadcast Audience Research Council, Mumbai)
The full story, with 28 moments, charts, people and 36 sources: glassbox.how/e/tvstationclear/history. The data lives in history.json.
Made with the Glassbox studio from this box's storyboard (window.glassbox.director). Free to reuse under CC BY 4.0.
| File | What | Size |
|---|---|---|
glassbox/reel.mp4 |
Reel / Short, with captions and soundtrack | 1080×1920 |
glassbox/video.mp4 |
YouTube video, with captions and soundtrack | 1920×1080 |
glassbox/slide-1…10.jpg |
Instagram carousel | 1080×1350 |
glassbox/thumb.jpg |
YouTube thumbnail | 1280×720 |
glassbox/cover.jpg |
Share card and repo social preview | 1200×630 |
glassbox/history-reel.mp4 |
“History in 10 moments” Reel / Short | 1080×1920 |
glassbox/history-slide-*.jpg |
History carousel | 1080×1350 |
glassbox/post.json |
Post copy and schedule used by the publish kit |
This box has no accounts and no ads, and it ships its own fonts and libraries. When you run it yourself it sends nothing anywhere. On glassbox.how, the site's /bar.js also loads Glassbox's analytics: Google Analytics to count visits (it asks first in the EU, UK and Switzerland, and stays off when your browser sends Global Privacy Control or Do Not Track) and ClickTrust to detect bots.
It remembers a few things in your own browser only, and never sends them anywhere:
| Browser storage key | What it holds |
|---|---|
tvstationclear.v1 |
Which chapters you have opened, your best quiz scores, and sound on or off. |
Exactly what each one sees is at glassbox.how/privacy.
- Code: MIT. Use it, change it, ship it.
- Explanations, text, images and videos (
glassbox.json,glassbox/): CC BY 4.0. Credit “Glassbox, glassbox.how/e/tvstationclear”. - Third-party parts keep their own licences: three.js (MIT), Geist, Instrument Serif (SIL OFL 1.1).
- The Glassbox name and logo aren't covered by either licence. See the terms.
Found a mistake? Open an issue. Corrections happen in public.
It's plain HTML, CSS and JavaScript. No build step and no dependencies. Run locally, it contacts no other website.
python3 -m http.server 8000Three.js and the fonts ship in vendor/ and fonts/, so it also works offline.
Then open http://localhost:8000.
| File | What |
|---|---|
index.html, css/app.css |
The page and its styles |
js/app.js, js/stage.js, js/ui.js, js/kit.js |
The shared Glassbox 3D engine: chapters, 3D stage, controls, quiz, video director |
js/station.js |
Shared models and numbers: people, pedestal cameras with teleprompters, the news set, dishes, satellite, van, the screen shader (mix and chroma key), satellite geometry and link-budget maths |
js/codec.js |
A tiny real MPEG-style coder: DCT, quantising, motion search, I/P/B frames |
js/chapters/*.js |
One file per chapter: the 3D model, controls, text, key terms, quiz and video scenes |
glassbox.json |
Title, question, explainer beats, key terms, browser storage and credits shown on glassbox.how |
reel in each chapter |
The storyboard the Glassbox studio records into short videos |
glassbox/ |
The published video, slides, thumbnail and post copy |
fonts/, vendor/three/ |
Self-hosted Geist and Instrument Serif (SIL OFL 1.1) and three.js (MIT) |