Originally published at: http://slms.wpengine.com/2016/01/echo-echo/
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 stationsign-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.[citation needed]
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.[1]
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 requiredFederal Communications Commission-USA/Industry Canada transmitter readings, and then turned off the power.[citation needed]
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[2] colloquially called snow (but resembling “bugs” following a TV-system technical improvement).[3] 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.