The evolution of television

TV sets have changed dramatically since they first became popular in the 1940s and 1950s. Although TV was invented in the 1920s, the equipment was expensive and the pictures were poor quality.

What started as a large box with limited broadcast channels and grainy images has evolved into high-definition flat screens with lots of channels and streaming options, such as Netflix and ShowMax.

The first TV sets used an antenna or aerial, and could only show black-and-white pictures.

The antenna would pick up TV programmes from broadcasting stations. A TV station could be many kilometres away, and the signal could still be received.

Colour TV and cable TV (a system that transmits TV programmes to the sets of subscribers by cable rather than by broadcast signal) started in the 1950s. Digital TV — the transmission of TV signals using digital rather than analogue methods — was established in the 1990s.

The main difference between analogue and digital is in how the signal is transmitted from the source to the TV in your home.

Analogue TVs transmit sound and video signals over airwaves in a manner similar to a radio signal. Each station has a single frequency over which to broadcast its analogue TV signal. You know these frequencies as channel numbers on your TV. Like radio signals, an analogue TV signal can be interrupted or experience interference. This can cause TV static or changes in colour, brightness and sound quality.

A digital TV signal transmits in “packets” of compressed data. Because it uses coded data, digital signals do not experience the same interference, or signal loss, that analogue TV signals do. This means that the TV picture remains clear.