How has TV tech evolved?

From CRT to 4K, OLED to HDR, understand the acronyms that have marked telly’s transformation

On 26 January 1926, Scottish inventor John Logie Baird demonstrated a working television at his London lab. However, few of us today would recognise what he called a ‘televisor’ as a TV. It used mechanically driven discs covered with lenses. These broke down light reflected by an object. The reflections were turned into an electrical signal and transmitted to a radio receiver that reconstructed an image of the object.

Baird’s mechanical television was quickly replaced by an electronic version, which made it easier to capture and transmit images. In 1931, Allen B DuMont’s cathode-ray tube (CRT) set the standard for television. Even the shift from black-and-white to colour TV in the late 1960s still used the same technology, cementing the place of the ‘tube’ in our homes for the rest of the 20th century.

Since the millennium, however, there’s been a TV tech explosion. Not only have these innovations kicked CRTs to the curb, they’ve been hard to keep up with. In 20 years we’ve gone from plasma TVs you could hang on your wall to OLEDs that are as little as 4mm thick. At the same time the images have gotten much sharper, with the development of 1080p or Full HD giving way to 4K and increasingly 8K.

Inside TVs

Organic light-emitting diode (OLED)

These TVs use a carbon-based film that glows when heated, so no backlight is needed. This light can also be controlled on a pixel-by-pixel basis for a sharper image.
✔ Displays are just millimetres thick
✔ Brilliant colours with high contrast
✘ Still very expensive to produce
✘ Small risk of screen burn

Liquid-crystal display (LCD)

These TVs shine light through a screen made up of liquid-crystal cells. Signals control each cell, making the crystals move and twist, letting different amounts and colours of light through.
✔ Extremely high- resolution image
✔ Accurately reproduces a range of colours
✘ Poor reproduction of black images
✘ Lower contrast and limited brightness

Light-emitting diode (LED)

A lot like LCDs, these TVs replace the fluorescent backlight with tiny LEDs. These can be arranged around the edge of the display, making for an even slimmer flat screen.
✔ LEDs give off natural-looking light
✔ They’re also more energy efficient
✘ Early versions had patchy colours
✘ Screen lighting can be inconsistent


A voltage is run through two thin sheets of glass containing plasma – ionised gas, often xenon or neon – that lights up when heated, making red, green and blue pixels glow.
✔ Great dark-room and wide-angle viewing
✔ Smooth picture with no motion blur
✘ It uses a lot of power
✘ Danger of screen burn

Cathode-ray tube (CRT)

Guided by magnets, beams of electrons are continuously fired through a glass vacuum tube at a screen covered in millions of red, blue and green dots to create an image.
✔ TV picture offered high colour contrast
✔ Reduced input lag, better for gaming
✘ CRT’s were big and very heavy
✘ Low resolution seems blurry today

(Image credits: Future PLC)

This article was originally published in How It Works issue 135

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