Industries in the Broadcasting and Telecommunications subsector include establishments providing point-to-point communications and the services related to that activity. The industry groups (Radio and Television Broadcasting, Cable Networks and Program Distribution, and Telecommunications) are based on differences in the methods of communication and in the nature of services provided. The Radio and Television Broadcasting industry group includes establishments that operate broadcasting studios and facilities for over the air or satellite delivery of radio and television programs of entertainment, news, talk, and the like. These establishments are often engaged in the production and purchase of programs and generating revenues from the sale of air time to advertisers and from donations, subsidies, and/or the sale of programs. The Cable Networks and Program Distribution industry group includes two types of establishments. Those in the Cable Networks industry operate studios and facilities for the broadcasting of programs that are typically narrowcast in nature (limited format, such as news, sports, education, and youth-oriented programming). The services of these establishments are typically sold on a subscription or fee basis. Delivery of the programs to customers is handled by other establishments, in the Cable and Other Program Distribution industry, that operate cable systems, direct-to-home satellite systems, or other similar systems. The Telecommunications industry group is primarily engaged in operating, maintaining, and/or providing access to facilities for the transmission of voice, data, text, sound, and full motion picture video between network termination points. A transmission facility may be based on a single technology or a combination of technologies. Establishments primarily engaged as independent contractors in the maintenance and installation of broadcasting and telecommunications systems are classified in Sector 23, Construction.