In article <k6npp8$olc$
1...@reader1.panix.com>,
danny burstein <
dan...@panix.com> wrote:
>In <
alpine.LNX.2.02.1...@darkstar.example.org> Michael
>Black <
et...@ncf.ca> writes:
>
>>>>
>>>> Nope. It's digital. A DECtape II.
>>>
>>> To me, it looks very much like an audio cassette in shape, and not like a
>>> (similar but different) DECtape II.
>>>
>>> In fact, if you look very closely, the tape not only look just like an
>>> audio cassette, but has the text "digital equipment corporation - maynard,
>>> massachusetts" and "1.0 MIL CERTIFIED DIGITAL CASSETTE" on it.
> ....
>>> cassettes, but have higher-spec tape for digital use; and it seems that
>>> this is what the camera uses: something with the form factor of an audio
>>> cassette but with a higher-spec "certified digital" tape.
>
>I don't know, in fact I doubt it was...
Well, it certainly seems - from the available documentation - that things
are essentially as I conclude.
Let me quote again from the TU-60 manual (at
http://bitsavers.trailing-edge.com/pdf/dec/decCassette/DEC-00-HTU60-C-D_TU60maint_Oct73.pdf):
"
1.2 CASSETTE RESTRICTIONS
It is extremely important that only DEC, 100 percent certified, Digital
Tape Cassettes be used on the TU60 tape drives. The "heavy base" tape
within the Digital Equipment Corporation Cassettes was specifically
chosen to be compatible with the high drive tensions of the TU60. In
addition, the head pressure pad material of the cassette has been
carefully selected to allow proper tape stacking. For optimal operational
characteristics, the dynamics of each tape drive require the use of only
Digital Equipment Corporation Cassettes.
DO NOT ATTEMPT TO USE AN AUDIO CASSETTE ON THE TU60 TAPE DRIVES. Since
the tape within an audio cassette is not designed to tolerate the high
drive tensions of the TU60, use of this type cassette will result in
extremely rapid deterioration of the tape and subsequent failure of the
drive due to excessive tape oxide deposits on the read/write head and
tape guides.
"
This clearly states that the "Digital Tape Cassettes" use a "heavy tape"
that "was specifically chosen to be compatible with the high drive
tensions of the TU60". In the next paragraph, the manual warns "DO NOT
ATTEMPT TO USE AN AUDIO CASSETTE ON THE TU60 TAPE DRIVES". This would not
be possible unless the tapes are substantially similar in form factor.
So the tape used in a TU60 is in substantially the same for factor as a
standard audio cassette (in fact a later section warns against using the
digital cassettes for audio - which also would not be possible unless they
were physically substantially similar), but uses a special "heavy tape" to
handle the high drive tension. And it so happens that in the picture of
the camera
(
http://www.kodak.com/US/images/en/corp/1000nerds/steveSasson/1_Camera.jpg),
there is a tape that looks very much like a standard audio cassette, but
marked "digital equipment corporation" as well as "Certified Digital
Cassette" - which rather strongly suggests that the cassette in the
picture is precisely the kind of digital cassette tape with "heavy tape"
that is described in the manual for the TU-60 tape drive.
>but a key difference
>later on beween standard "audio" (or, for that matter, video)
>tapes and the data ones was that...
>
>... was that the audio/video ones were "locked", so to speak,
>into the spools so that the tape would remain in place.
>
>The data ones, on the other hand, were just loosely lying
>on the spindles, and if the drive didnt detect the little
>foil tab saying "please stop now", the tape would actually
>come off the spindle and fly loosely over to the takeup.
>
>- the reason for this was to prevent any stretching of
>the tape, which would cause errors in trying to read them.
>
>I know this was standard by 1985 or so when I was doing
>tape backups. I don't know about earlier.
The Kodak camera in question was in 1975, so 10 years earlier than the
experience you're relating to. Anyway, the manual (linked to above, and in
my earlier post) contains lots of information including drawings and the
layout of the tape.
Best wishes,
// Christian