Cable delivery of television started as a way to improve reception. Today, cable television is popular because of the wide variety of programming it can deliver. Many systems now provide more than 100 channels of programming. Typically, a cable television company receives signals relayed from a communications satellite and sends those signals to its subscribers. The first transatlantic television broadcast was accomplished by such a satellite, called Telstar, on July 10, 1962.
Some television viewers use small satellite dishes to receive signals directly from satellites.
Most satellite-delivered signals are scrambled and require a special decoder to receive them clearly. The most noticeable difference between the current system and the HDTV system is the aspect ratio of the picture. HDTV also provides higher picture resolution and high quality audio. Each frame of video consists of 720 or 1,125 horizontally scanned lines instead of the current 525. Furthermore, the lines are scanned sequentially, not interlaced as they are now.