e. By 1937, RCA had rectified their television system but faced new problems. The television industry could not agree on a common standard. In 1936, the Radio Manufacturers Association (RMA), which RCA backed, appointed a committee to approve a system. In 1937, they rubber-stamped RCA's 441-line 30 frames per second (fps) proposal. However, RCA's iron grip on the industry stirred controversy and, in 1940, the FCC chairperson intervened to order additional study. It downgraded NBC, which had been broadcasting since the 1939 World's Fair, from a licensed station to an experimental station until the difficulties could be resolved. A flurry of hearings ensued. On April 30, 1941, the FCC approved an amplitude- modulated monochrome television system. It defined a video frame to contain 525 scanning lines. Each second, thirty such frames were to be transmitted and synchronized with frequency-modulated audio. The system was analog; the electron flow that it sent as a signal was analogous to the original waveform. The History and Technology of Analog Video As part of the standard, the FCC determined the range of frequencies to allocate to each television channel. They specified that monochrome television signals be modulated onto radio frequency (RF) carrier waves with bandwidths of 4.2 MHz. Each channel would occupy 6 MHz of bandwidth. Audio information would be transmitted above video starting at 4.5 MHz. Unused bandwidth above the audio and below the video would protect the signal from interfering with other channels. On July 1, 1941, the FCC licensed NBC and the newly formed Columbia Broadcasting System (CBS) to operate commercial television stations in the U.S. They promptly began broadcasting. In 1945, the FCC allocated spectrum space for 13 television channels, all in the very- high frequency (VHF) band that occupies the spectrum between 54 and 216 MHz. Also interspersed in this band were FM (frequency modulation), mobile and emergency radio, and air navigation signals. Eventually, it eliminated channel one and lef