11 Dec
2005
11 Dec
'05
5:01 p.m.
Speaking of audio cassette storage, I received this inquiry
to my web. Click the link to hear the data he has... What's
odd to my ear is that the data seems to be packeted between
carrier. Might this be someone's custom data, as opposed to
ordinary program load/save?
As for why MP3s work fine and .WAV is unnecessary, MP3's
compression divides the signal into ~32 frequency bands, then
encodes the amplitude of those over time. The typical
two-frequency sine modulation used by cassette data recorders
probably fits quite well into those two bins, and MP3 would
recreate the simple sine waves quite well.
After all, some of the hardware/software decoders within the
classic PCs (as well as their emulators) may have only used
the timings of zero-crossings, so they aren't very sensitive
to perfect reproduction of the waves.
- John
Date: Sat, 10 Dec 2005 16:11:34 +0100
From: Paul Geisler <paul.geisler at web.de>
To: jfoust at threedee.com
Subject: unknown data tape
hello.
i found some old tapes i know nothing about ecept by title it may contain interesting
information, and came from merely professional use.
the tapes are recorded on standard compact casette but with some dedication to data
recording for example switchable write protection etc.
the label reads "T 300 Certified Data Casette".
i capture the contents by stereo tape recorder, found both channels nearly equal so guess
this mono, mixed them. the tapes are two-sided like normal audio ones.
a strange thing is, that the recording is in small "packets", with empty tape
inbetween. i first guessed it is only "empty formatted" tape, but the data
packets seem to contain a varying length of information. still strange to waste more than
a half of material this way? also strange the packets are ending with a simple tone,
instead are headed with, so maybe this is used backward at original drives.
here is a seven packet sample some minutes after beginning of one tape; all tapes seemed
to have this same "format" from start to some end location which is not the real
tape end:
http://hirnsohle.de/test/datenSnipplet.wav (16bit mono microsoft-wav 624kb)
i would be very happy if you had any idea how to look at the contents (if any).. i'm
currently searching for some sofware "tape modem". i know such things for C64
datasette tapes, so maybe you know some universal program, where different emulations or
flexible parameters can be used to find a matching demodulation/decoding?
thanks very much & best regards
Paul Geisler
11 Dec
11 Dec
5:22 p.m.
On 12/11/2005 at 11:01 AM John Foust wrote:
Speaking of audio cassette storage, I received this
inquiry
to my web. Click the link to hear the data he has... What's
odd to my ear is that the data seems to be packeted between
carrier. Might this be someone's custom data, as opposed to
ordinary program load/save?
I don't know about the content, but units that used these cassette tapes to
simulate a paper tape reader or punch were not uncommon in the early-to-mid
70's. I used to have one with two decks and was block formatted and
searchable--in either direction. Top speed IIRC, was about 2400 baud. For
a time, I used it with an early editing terminal as a rudimentary word
processing system.
Cheers,
Chuck
7:14 p.m.
I don't know about the content, but units that
used these cassette tapes to
simulate a paper tape reader or punch were not uncommon in the early-to-mid
Probably the most common was a verstion of the TI Silent 700. It had a
box fitted on top containing 2 tape drives and a handful of boards of
logic to control them. You could use them like punches or readers
(save/load data either locally or to the line, copy data between the 2
tapes, 1 character at a time I think, etc).
As an aside, I bought a Microwriter the other day. It contains an 1802
processor. While looking for the user manual for that chip (I found it),
I came across the manual for the RCA developemnt sysetm for the 1802.
Said manual contains scheamtics and ROM sources, BTW. And in the same box
were the binary paper tapes for the editor and assembler and a cassette
containing the same stuff to be read on such a Silent 700
Another format (or at least I think it's another format) used the full
width of the tape in one go and recorded 2 tracks. A pulse on one track
was a '0'. A pulse on the other track was a '1'. A pulse on both tracks
together was some kind of marker. The HP9830 uses this format, the
'maker' being na end-of-byte marker. I think other machines used it for
end-of-file or similar.
-tony
9:37 p.m.
On 12/11/2005 at 7:14 PM ard at p850ug1.demon.co.uk wrote:
Probably the most common was a verstion of the TI
Silent 700. It had a
box fitted on top containing 2 tape drives and a handful of boards of
logic to control them. You could use them like punches or readers
(save/load data either locally or to the line, copy data between the 2
tapes, 1 character at a time I think, etc).
Funny you should mention that. When I first got my MITS 8800, one of the
first problems was what to do for offline storage. ASR33's were pretty
expensive, so audio cassette was a natural. I used the modem board out of
a Silent 700 to work with a cheap audio drive. It wasn't fast, but it
worked. I eventually hooked up the recorder's motor control so the 8800
could start and stop the tape. I recall that BASIC for the system was
furnished on both paper tape and a (white case) audio cassette. But the
Silent 700 modem did double duty for me--it let me dial into the mainframe
at work as well as record and play back data tapes.
Cheers,
Chuck
5:22 p.m.
New subject: unknown data tape
----- Original Message -----
From: "John Foust" <jfoust at threedee.com>
To: <cctalk at classiccmp.org>
Sent: Sunday, December 11, 2005 6:01 PM
Subject: Fwd: unknown data tape
Speaking of audio cassette storage, I received this inquiry
to my web. Click the link to hear the data he has... What's
odd to my ear is that the data seems to be packeted between
carrier. Might this be someone's custom data, as opposed to
ordinary program load/save?
If I would have to make a guess, I would say "ECMA 34" format. It sounds
a
lot like the cassettes used on Philips minis like the P300, P400, P6000 etc.
ISTR that the recording was serial, recording speed 6000 bps, one track,
with 250K bytes on each side.
Nico
6970
days inactive
6970
days old
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ard＠p850ug1.demon.co.uk -
cclist＠sydex.com -
jfoust＠threedee.com -
nico＠farumdata.dk