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,