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Direct-broadcast satellite (DBS) is a type of artificial satellite which usually sends satellite television signals for home reception. The type of satellite television which uses direct-broadcast satellites is known as direct-broadcast satellite television (DBSTV) or direct-to-home television (DTHTV). This has initially distinguished the transmissions directly intended for home viewers from cable television distribution services that are sometimes carried on the same satellite. The term DTH predates DBS and is often used in reference to services carried by lower power satellites which required larger dishes (1.7 m diameter or greater) for reception. In Europe, prior to the launch of Astra 1A in 1988, the term DBS was commonly used to describe the nationally commissioned satellites planned and launched to provide television broadcasts to the home within several European countries (such as BSB in the United Kingdom and TV-Sat in Germany). These services were to use the D-Mac and D2-Mac format and BSS frequencies with circular polarization from orbital positions allocated to each country. Before these DBS satellites, home satellite television in Europe was limited to a few channels, really intended for cable distribution, and requiring dishes typically of 1.2m. SES launched the Astra 1A satellite to provide services to homes across Europe receivable on dishes of just 60-80 cm and, although these mostly used PAL video format and FSS frequencies with linear polarization, the DBS name slowly came to applied to all Astra satellites and services too. ==Terminology confusion== As a technical matter, DBS (also known by the International Telecommunication Union as Broadcasting Satellite Service, or BSS) refers only to services transmitted by satellite in specific frequency bands: 11.7-12.2 GHz in ITU Region 3 (Asia and Australia), 10.7 - 12.75 GHz in ITU Region 1 (Europe, Russia and Africa), and 12.2-12.7 GHz ITU Region 2 (North and South America). In 1977, the ITU adopted an international BSS Plan under which each country was allocated specific frequencies at specific orbital locations for domestic service. Over the years, this plan has been modified to, for example, accommodate new countries, increase coverage areas, and reflect digital (rather than analog) technology. At present, numerous countries have brought into use their BSS Plan allocations. By contrast, DTH can apply to similar services transmitted over a wider range of frequencies (including standard and ) transmitted from satellites that are not part of any internationally planned band. Nonetheless, the term DBS is often used interchangeably with DTH to cover both analog and digital video and audio services (including video on demand and interactive features) received by relatively small dishes (less than 1 meter). A "DBS service" usually refers to either a commercial service, or a group of free channels available from one orbital position targeting one country. In certain regions of the world, especially in North America, DBS is used to refer to providers of subscription satellite packages, and has become applied to the entire equipment chain involved. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Direct-broadcast satellite」の詳細全文を読む スポンサード リンク
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