On this day, 34 years ago, on December 7, 1991 (November 2, 1991 in the lunar calendar), the United States developed an all-digital TV system. In early December 1991, Summit Electric and AT & T announced that they had jointly developed an all-digital TV system. This digital TV system will soon replace the high-definition TV system currently under development. Digital television systems can send non-interference signals to a wider geographical area than ordinary broadcast systems or high-definition television systems. It can provide large-screen images like high-definition TVs have, and has a variety of other uses, but at a much lower cost than high-definition TVs. Digital signals can be transmitted by satellites and terrestrial transmission towers, and can be easily converted to any television format, so that they can be received by a variety of televisions across system boundaries.