In <[log in to unmask]>, on 03/02/00
   at 09:50 PM, Alan Eugene Davis <[log in to unmask]> said:

>I connected a Microtek X6EL to the SCSI2 channel of an Adaptec
>2940U2W.  The scanner is currently the only device on that card,
>and is connected through the DB25 to DB25 cable supplied with the
>scanner, through a converter/bracket from a 50pin internal cable.

>I installed this scanner before I saw the terminator in the box,
>without the terminator.  After recompiling the kernel to
>recognize SCSI generic devices, I installed relevant packages on
>my Debian GNU/Linux system, the SANE-related packages.

>After running

>      $ scanimage --list-devices

>the scanner was identified, and, ever since, there has never been
>a need to fiddle---whenever I start the software, either through
>The GIMP or via xscanimage itself, the scanner works flawlessly.

>After I discovered the DB25 SCSI terminator in the packing, I
>installed it.  Not only will the scanner not work correctly with
>it installed; but the terminator is  quite warm to the touch.
>Since I removed the terminator, the scanner has been performing
>flawlessly.

>Can someone explain the seeming anomalous behavior regarding  the
>terminator?  I can only  think  that the Adaptek 2940U2W doesn't
>need a terminator, while perhaps the Adaptec 2902E/I does need
>it.

>What gives?

>Alan Davis



>--
>[log in to unmask]

Alan:
The SCSI bus requires proper termination to operate correctly. The
normal configuration is to terminate each end of the bus. Some
devices have terminators built in, while others require external
terminators. The same is true of the cards, although most have
terminators on board. The terminators dissipate considerable
power, so warm is ok.

As a note, some SCSI cards allow both internal and external
devices. In this case, the boards termination should be disabled,
and the ends of both device chains terminated.


jan lambert

Old Navy Proverb: If it works, don't fix it.
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