[QuadList] QuadList Digest, Vol 60, Issue 11

[Dennis Degan]

		I offered:

> That may have been true at the time Brigadoon was fed to stations, but starting in 1977, AT&T was in the process of replacing all video terminal equipment with a multiplex baseband system that not only provided stations with high fidelity audio, it was capable of feeding stereo audio to stations as well.  Before baseband multiplexing, TV audio was sent SEPARATELY on 5k phone lines.  This old method of transmission had a number of disadvantages.  Multiplexing provided high-quality (50-15k Hz) low-noise audio with stereo as an option and guaranteed video-to-audio synchronization.  This was because the audio travelled the same path with the video.  It didn't last because networks changed over to satellite distribution in the early '80's, making AT&T's microwave/coaxial cable distribution obsolete.

		On Jun 21, 2013, at 1:11 PM, TQ wrote:

> Was this done with SiS?

		I say:

	No, "Sound In Sync" was more of a European technique and was used later in satellite transmission.  "Baseband Multiplex" used two simple subcarriers, one for each audio channel, to carry the audio with the video.  As I recall, the primary audio used 5.3MHz while the second (optional) carrier was 6.2MHz.  I may not have the carrier frequencies right, but I know they were both above the NTSC color subcarrier frequency of 3.579MHz.

			Dennis Degan, Video Editor-Consultant-Knowledge Bank
					NBC Today Show, New York


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