Re: ADB Switchbox requirements

[ToasterKing <toasterking@SPLATbigfoot.com>]

In article <20031010064354.15639.00000094@mb-m13.aol.com>, Michael J.
Mahon <mjmahon@aol.com> wrote:

> The controller protocols are not designed for hot-swapping either.
> That means that the switched device(s) will not have been properly
> "introduced" to the controller, and will not, in general, be initialized
> as the controller would like.  This can result in spurious message
> delivery and peculiar reactions by the host system.

That does help explain its operation.  As long as the ADB devices were
present when the system was booted and they have not changed since
then, I've never had a problem with a system recognizing the devices it
had already reocgnized at boot.  Thanks for the info.

> >  A standard ADB cable
> >should work fine.  Hint: If you don't have spares, you can also use an
> >S-Video cable in place of an ADB cable -- they're identical as far as
> >connectors and shielding.
> 
> Well, not quite identical--when you use an S-Video cable for ADB,
> you put the ADB signalling on one of the internal shields, and +5v
> on a center conductor.  It works, since ADB is low speed, but
> it isn't made like an ADB cable.

I stand corrected -- so shielding isn't the same.  If that's the case,
I can see how the shielding of an S-Video cable wouldn't be as
effective, since the shield is not carrying signal ground.  That
doesn't seem to be too much of an issue, though.  Like you said, ADB is
low-speed and as such isn't as prone to noise or even very short logic
glitches.  Apple also says the maximum cable length of the ADB bus
should be 5 meters.  In the past, I've used cabling about 6.1 meters in
length involving 2 devices plus a switchbox (that's cabling to one
computer), and 3.7 meters of that was S-Video cabling -- and it still
always worked fine.  But thanks for the heads-up.

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