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<TITLE>sane-devel: Re: HP 7400c info / Minolta Scan Dual II</TITLE>
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<META NAME="Author" CONTENT="Oliver Neukum (Oliver.Neukum@lrz.uni-muenchen.de)">
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<META NAME="Subject" CONTENT="Re: HP 7400c info / Minolta Scan Dual II">
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<H1>Re: HP 7400c info / Minolta Scan Dual II</H1>
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<!-- received="Thu May 3 02:42:04 2001" -->
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<!-- isoreceived="20010503094204" -->
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<!-- sent="Thu, 3 May 2001 11:51:04 +0200" -->
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<!-- name="Oliver Neukum" -->
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<!-- email="Oliver.Neukum@lrz.uni-muenchen.de" -->
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<!-- subject="Re: HP 7400c info / Minolta Scan Dual II" -->
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<!-- id="01050311510400.02042@idun" -->
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<!-- inreplyto="6e.a3b80a0.282275fc@aol.com" -->
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<STRONG>From:</STRONG> Oliver Neukum (<A HREF="mailto:Oliver.Neukum@lrz.uni-muenchen.de?Subject=Re:%20HP%207400c%20info%20/%20Minolta%20Scan%20Dual%20II&In-Reply-To=<01050311510400.02042@idun>"><EM>Oliver.Neukum@lrz.uni-muenchen.de</EM></A>)<BR>
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<STRONG>Date:</STRONG> Thu May 03 2001 - 02:51:04 PDT
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<P>
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<LI><STRONG>Next message:</STRONG> <A HREF="0043.html">Ulrich Deiters: "Re: Canon backend"</A>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0041.html">EdHamrick@aol.com: "Re: HP 7400c info / Minolta Scan Dual II"</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0041.html">EdHamrick@aol.com: "Re: HP 7400c info / Minolta Scan Dual II"</A>
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0052.html">EdHamrick@aol.com: "Re: HP 7400c info / Minolta Scan Dual II"</A>
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<HR NOSHADE><P>
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<P>
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On Thursday, 3. May 2001 10:51, you wrote:
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<BR>
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<EM>> In a message dated 5/3/2001 3:19:34 AM EST, <A HREF="mailto:moitinho@civil.ist.utl.pt?Subject=Re:%20HP%207400c%20info%20/%20Minolta%20Scan%20Dual%20II&In-Reply-To=<01050311510400.02042@idun>">moitinho@civil.ist.utl.pt</A>
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</EM><BR>
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writes:
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<BR>
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<EM>> > I have read the arguments in favour of different drivers, you don't need
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</EM><BR>
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<EM>> > to try to explain, but I still don't understand why (for instance) the
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</EM><BR>
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<EM>> > usb-storage driver doesn't work (at least id didn't). Just my problem of
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</EM><BR>
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<EM>> > thinking that I understand what I don't.
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</EM><BR>
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<EM>>
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</EM><BR>
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<EM>> There's no good reason why a single driver shouldn't serve
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</EM><BR>
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<EM>> as a scsi->usb device driver for all devices that need to look
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</EM><BR>
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<EM>> like a scsi device to higher level routines.
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</EM><BR>
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<P>Our disagreement seems to be rather in the type of scanners that should
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<BR>
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appear as scsi devices to user space.
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<BR>
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If I understand Ed correctly, to him that would be all of them.
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<BR>
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<P><EM>> Oliver claims this would be too hard to write, but I've done it
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</EM><BR>
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<EM>> on Windows and Mac OS and it isn't hard. The upper levels
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</EM><BR>
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<EM>> of VueScan think they're working with SCSI scanners, and
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</EM><BR>
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<EM>> at the lowest level I translate scsi commands to USB
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</EM><BR>
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<EM>> commands. The trick is to design the driver to do this from
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</EM><BR>
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<EM>> the start. This works today on Windows and Mac OS with
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</EM><BR>
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<EM>> HP, Epson, Avision, Acer, and AGFA USB scanners. I did
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</EM><BR>
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<EM>> the same thing with Firewire scanners on Windows, since
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</EM><BR>
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<EM>> they also encapsulate scsi commands on Firewire (SBP2
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</EM><BR>
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<EM>> protocol). Someone already did a generic scsi->firewire
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</EM><BR>
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<EM>> driver on Linux, and a similar scsi-usb driver is all that's needed.
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</EM><BR>
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<P>Firewire is a better design. There is no question about that.
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<BR>
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USB has no common protocol for transfering SCSI commands.
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<BR>
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In fact I know of _six_ incompatible protocols to do that.
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<BR>
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The attempt to unify them leads to a monster like usb-storage.
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<BR>
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I wanted to add the microtek protocol to usb-storage, but Matt vetoed that.
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<BR>
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<P><EM>> Note that the advantage of using generic scsi->usb and
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</EM><BR>
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<EM>> scsi->firewire drivers is that there isn't any need to set
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</EM><BR>
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<EM>> up configuration files specifying which scanners (and
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</EM><BR>
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<EM>> what type of scanners) are on the system. The nice
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</EM><BR>
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<EM>> part of scsi is that it's possible to poll each device to find
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</EM><BR>
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<EM>> out what kind of device it is, instead of depending on the
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</EM><BR>
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<EM>> user to set this up (this is a lot more user-friendly). This
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</EM><BR>
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<EM>> is how VueScan works.
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</EM><BR>
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<P>I could trivially merge microtek and hp5300 to a common driver.
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<BR>
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However there would still be the generic driver (scanner.c) and
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<BR>
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the two drivers currently under development for even stranger scanners.
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<BR>
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Reducing the number of drivers from 5 to 4 isn't IMHO worth the trouble.
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<BR>
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Unless you go to one, you need to look it up anyway, thus simplicity in
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<BR>
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kernel is more important.
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<BR>
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<P>As for configuration, loading a driver for your usb scanner is the same
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<BR>
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trouble as loading a driver for the controller your scsi scanner is attached
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<BR>
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to.
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<BR>
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After that for microtek and hp5300 then you can probe as for conventional
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<BR>
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scsi. Generic usb scanners are a problem though.
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<BR>
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<P><EM>> This driver the kind of thing I'd assign a college intern or
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</EM><BR>
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<EM>> beginning programmer to do - it's not hard. If nobody on
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</EM><BR>
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<EM>> this list has any kernel programming experience, I'll do it
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</EM><BR>
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<EM>> myself in a month or two as soon as I finish some higher
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</EM><BR>
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<EM>> priority tasks in VueScan. However, if I write it, I plan to
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</EM><BR>
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<EM>> sell it (it won't be open source). If someone wants to
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</EM><BR>
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<EM>> write it and make it open source, I'd be happy to provide
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</EM><BR>
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<EM>> them the technical assistance they'd need to get it working
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</EM><BR>
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<EM>> with a wide range of usb scanners.
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</EM><BR>
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<P>For generic scanners you _could_ go the easy route.
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<BR>
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Emulate INQUIRY based on a table of vend./prod. ids and
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<BR>
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map read/write over usb to SCSI_READ/SCSI_WRITE.
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<BR>
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<P>It can be done. Even the unusual scanners could be handled with vendor
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<BR>
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specific commands. However at some point you end up with a scsi interpreter
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<BR>
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in kernel.
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<BR>
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The resulting driver would end up much more complicated than generic scanner,
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<BR>
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which is beautifully simple.
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<BR>
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I am quite convinced that it would not be accepted into the kernel, even be
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<BR>
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it open source.
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<BR>
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<P>What we need to solve is the problem of identifying usb device with a device
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<BR>
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node with IMHO a generic ioctl. And someone should sacrifice his keyboard for
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<BR>
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fixing autoloading for scanner.o
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<BR>
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<P> Regards
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<BR>
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Oliver
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<BR>
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<P><PRE>
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--
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Source code, list archive, and docs: <A HREF="http://www.mostang.com/sane/">http://www.mostang.com/sane/</A>
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To unsubscribe: echo unsubscribe sane-devel | mail <A HREF="mailto:majordomo@mostang.com?Subject=Re:%20HP%207400c%20info%20/%20Minolta%20Scan%20Dual%20II&In-Reply-To=<01050311510400.02042@idun>">majordomo@mostang.com</A>
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</PRE>
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<!-- next="start" -->
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<LI><STRONG>Next message:</STRONG> <A HREF="0043.html">Ulrich Deiters: "Re: Canon backend"</A>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0041.html">EdHamrick@aol.com: "Re: HP 7400c info / Minolta Scan Dual II"</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0041.html">EdHamrick@aol.com: "Re: HP 7400c info / Minolta Scan Dual II"</A>
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<!-- nextthread="start" -->
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0052.html">EdHamrick@aol.com: "Re: HP 7400c info / Minolta Scan Dual II"</A>
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<SMALL>
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<EM>
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This archive was generated by <A HREF="http://www.hypermail.org/">hypermail 2b29</A>
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: <EM>Thu May 03 2001 - 02:42:50 PDT</EM>
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</EM>
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