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The Indian-head test pattern is a black and white television test pattern which was introduced in 1939 by RCA of Harrison, New Jersey as a part of the RCA TK-1 monoscope. Its name comes from the original art of a Native American featured on the card. It was widely used by television stations worldwide during the black and white TV broadcasting era before 1970. == As television broadcasting ritual == The Indian-head test pattern became familiar to the large Post–World War II baby boom TV audiences in America from 1947 onwards; it would often follow the formal television station sign-off after the United States national anthem. The Indian Head was also used in Canada, following the Canadian national anthem sign-off in the evening. It was also used by Rhodesia Television (RTV) during British colonial times (varying between Northern and Southern Rhodesia), as the pattern was displayed following the playing of ''God Save the Queen''. This test pattern was later used by Venezuelan TV channel Venevision, in conjunction with the RMA Resolution Chart 1941, in the mid and late 1970s before the Venezuelan anthem (''Gloria al bravo pueblo''). Telesistema Mexicano (now Televisa) stations also used this test pattern until the late-1960s immediately after a Mexican National Anthem (''Mexicanos, al grito de guerra'') film. In Sweden the Indian head was used in test transmissions from the Royal Institute of Technology from 1948 until November 1958 when it was replaced by the Sveriges Television test card. It was also used in Brazil by Rede Tupi from the launch until the transformation in colour. The Indian-head pattern could variously be seen: after sign-off but while the station was still transmitting; while transmitting prior to a typical 6 AM formal sign-on; or even during the daylight morning hours on newer low budget stations, which typically began their broadcast day with midday local programming around 10 or 11 AM.〔 "Every television station, prior to its actual broadcasting period, transmits a test pattern for the purpose of permitting set owners to adjust their receiver controls for optimum reception." The article also states that television programming (in 1949) was only a few hours each evening. The Indian-head test pattern was built into the RCA "monoscope" tube, a 2F21, which acted as a complete replacement for the TV camera.〕 During the late 1950s the test pattern gradually began to be seen less frequently, after fewer sign-offs, on fewer stations, and for shorter periods in the morning, since new and improved TV broadcast equipment required less adjusting. In later years the test pattern was transmitted for as little as a minute after studio sign-off while the transmitter engineer logged required Federal Communications Commission-USA/Industry Canada transmitter readings, and then turned off the power. Towards the end of the Indian-head TV era (around the late 1970s), there was no nightly test pattern on some stations, typically when automatic logging and remote transmitter controls allowed shutdown of power immediately after the formal sign-off. After an immediate transmitter power off, in lieu of the Indian-head test pattern and its sine wave tone, a TV viewer heard a loud audio hiss like FM radio interstation noise and saw the video noise〔TV/video "snow" noise is unrelated to "White noise". TV "snow" vaguely resembled precipitating snow at night (in the UK, anyway). White noise is an analogy to the flat-amplitude continuous-frequency spectrum of white light, as opposed to pink noise that gradually increases in strength toward the red or bass end of the audio frequency spectrum.〕 colloquially called ''snow'' (but resembling "bugs" following a TV-system technical improvement).〔This video noise resembles fast-flickering white snow precipitation on a black background on TV systems which use positive video modulation, however views of systems using negative modulation (such as NTSC TV-system viewers in the USA, Canada, and Japan) saw an impression of fast-flickering black "bugs" on a white background. The NTSC committee chose negative video modulation, because flecks of white "snow" are more noticeable and annoying than flecks of black "bugs".〕 Audio and video noise received on Indian-head era TV sets respectively indicated the absence of analog aural and visual broadcast carriers. Consumer TVs typically did not have a no-signal noise muting and blanking feature until the late analog TV period. The Indian head pattern was also best known as an original for WGN-TV in Chicago, Illinois in its early days. When USA broadcasters transitioned to color television, the SMPTE color bars superseded the black-and-white test pattern image. 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「Indian-head test pattern」の詳細全文を読む スポンサード リンク
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