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From: Patent Tactics, George Brock-Nannestad In reply to > [log in to unmask] Jerome Hartke wrote > While testing 4 mm and 8 mm helical scan tapes some years ago, we > conducted pseudo-wear tests that consisted of multiple passes. The area > within each pass remained satisfactory, but residue accumulated at each > end of the wear region. This residue caused drop-outs and read errors, > and consisted of particles from the magnetic coating itself. Such tapes > had significant problems if the recording area was subsequently expanded > outside of the wear test region. > ----- Ray Dolby has recounted that the only reason that his group at AMPEX were able to record video signals during their first experiments in the 1950s was that they obtained a polishing of the tape surface during the multitudinous very fast passes over the tone heads. The tone heads were worn at the time, for sure, but the improved tape-to-head contact became an established fact, later documented by experiment. Obviously tape was a very different matter then. Kind regards, George