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#6
09-12-2004, 12:06 AM
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Actually the "Apple" tube gun generated two beams, the main beam to "paint" the picture on the phosphor screen and the "index" beam. The phosphor layer contains the RGB stripes and also an index stripe laid over all red stripes. The index beam is modulated with a 7.4Mhz signal to mark it. The secondary emission from the index stripe is used to give a constant indication of the position of the writing beam.
In the Apple tube it didn't make any difference what color was shown on the screen, black or white, the system always knew where the beam was located. There is a good report I have posted on the operation of the system here: http://www.myvintagetv.com/Apple%20P...report_458.pdf ChuckA
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