Broadcast TV operates on analog television waves such as PAL and NTCS systems. Most of these broadcasting signals were originally in monochrome and later developed into full-color displays. Using this technology, the sound and visual components of what is observed at the viewer's end are transmitted separately in unison using an antenna. Analog TV sets have built-in analog receivers that relay both the visual and audio aspects of the signal in the form of radio waves to the screen and TV speakers respectively.
Digital television operates on digital signals. This type of transmission is encouraged for home television, as it supports a broader range of pictures mainly divided into three groups: high-definition television (HDTV), enhanced-definition television (EDTV) and standard-definition television (SDTV). Digital televisions combine picture features such as aspect ratio and size as well as interlacing to produce better-quality images. In digital television, both the visual and audio components of the transmission are combined into one signal, unlike the analog transmission where the signal is combined to one radio signal and then separated back again.
Digital TV signals occupy less space as opposed to analog TV in transmission, therefore leaving more room for more TV stations in a particular region. Digital TV comes with an added ability of multicasting that allows broadcasters to transmit multiple programs simultaneously. With digital transmission comes improved picture quality as well as its size. Generally, digital television is superior to analog television, and some countries including the U.S. have decided to completely switch public television to this improved system.
Broadcasters and the government have taken steps to convert broadcasting from analog to digital TV. This involves large investments in transmission equipment and further expenditure from the viewer for buying TV sets with digital tuners but with added advantages. Another reason for making this switch is to free the original radio waves for use by the police, fire and rescue teams as well as companies that provide wireless services.