cable TV Cable TV was invented in 1948. The cable industry as we know it really came into being in the late 1970s, when specialty channels like HBO and ESPN put their signals on satellites and became nationwide cable networks. By the late 1990s, nearly 70 percent of all households were cable TV subscribers, and shows that appeared exclusively on cable were as popular as the regular network shows.
digital TV Analog broadcasting uses radio waves to transmit television signals. Digital broadcasting transmits digital signals and uses data compression to occupy far less bandwidth. Prior to 1996, television broadcasting was strictly analog.
In 1996, the government gave every TV station in America an extra channel free of charge to use for digital broadcasting. The plan was for all stations to have a digital signal on the air by 2003 and for all analog channels to be shut off by 2006.
After two years of experimental broadcasts, digital broadcasting was officially launched in 1998. One year later, 69 stations had a digital channel on the air. The first digital television sets and set-top converter boxes went on the market in 1997.
Some stations planned to use their digital channel to showcase the emerging high definition format. Other stations believed that multicasting was a good way to use the extra bandwidth. Multicasting makes it possible for up to six digital subchannels to share a single frequency, where previously only one analog channel could fit. TV stations began multicasting in 1999.
high definition TV A standard TV uses a resolution of 525 lines. A high definition TV is a digital TV with a resolution of 720 or 1,080 lines. The additional lines create a sharper, clearer picture. The technology was developed in Japan, and the first HDTV sets in America went on sale in 1998.
Broadcasting in HD requires a digital signal and special studio equipment. In 1996, the first station to broadcast in HD was also the first station to broadcast digitally: WRAL-HD in Raleigh, North Carolina. In 1999, CBS was the first network to regularly broadcast primetime shows in HD.