Apple SCSI

Don THX1138 at
Mon Sep 4 01:40:33 CDT 2006

Roy J. Tellason wrote:
> On Sunday 03 September 2006 03:08 pm, Don wrote:
>> I assume a good goal is to minimize *connections* wherever
>> possible.
> Why?

- connections give rise to *broken* connections (i.e. cable
gets bumped, etc.)
- connectors almost invariably add C
- connectors often introduce impedance mismatches (not from
the connector, per se, but what's behind it)

>> E.g., how much grief can I expect going *through* the slide
>> scanner with DB25 coming in and Centronics going out?
> I'm not sure that you even _can_ do this without seeing some detailed 
> technical info on the scanner.

Scanner has DB25 and Centronics connectors.  Obviously, an attempt
to be compatible with a variety of different applications.
They are no doubt wired AS IF they were two "identical" connectors
with the scanner itself sitting *logically* between them (though
I have seen this PHYSICALLY violated so often on SCSI devices
that I wouldn't make any bets on it!).

So, it *suggests* running *into* the slide scanner on one connector
and *out* (to the next downstream device) on the *other* connector.
(scanners often only have a single connector which makes putting
more than one on a given SCSI chain a bit of a chore)

>> Is this just effectively a "DB25-Centronics" adapter with a device tap in
>> the middle?
> No way to tell without looking...

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