[Steve D.]

Thanks to all for the various explanations. However,I'm still a bit puzzled? The 21FB and 21FJ were all-sulphide tubes. As I understand it this provided higher brightness levels and provide a red phosphor that was nearly equal in brightness to the green and blue phosphors. Were the tubes with "rare earth phosphors" different from the "all sulphide" tubes? Is sulphide a reference to the red phosphor only? I understand that the term "rare earth phosphor" is a chemical/scientific reference. But its almost magical and mysterious sound compared to the dull sounding term "sulphide" was used frequently in ads to hype the higher brightness and more vibrant color.