監視カメラ
Closed-circuit television was used as a form of pay-per-view theatre television for sports such as professional boxing and professional wrestling, and from 1964 through 1970, the Indianapolis 500 automobile race. Boxing telecasts were broadcast live to a select number of venues, mostly theaters, where viewers paid for tickets to watch the fight live. The first fight with a closed-circuit telecast was Joe Louis vs. Joe Walcott in 1948. Closed-circuit telecasts peaked in popularity with Muhammad Ali in the 1960s and 1970s, with "The Rumble in the Jungle" fight drawing 50million CCTV viewers worldwide in 1974, and the "Thrilla in Manila" drawing 100million CCTV viewers worldwide in 1975. In 1985, the WrestleMania I professional wrestling show was seen by over one million viewers with this scheme. As late as 1996, the Julio César Chávez vs. Oscar De La Hoya boxing fight had 750,000 viewers. Closed-circuit television was gradually replaced by pay-per-view home cable television in the 1980s and 1990s.