I have seem some "noname" so called "active" cables that do not have the
correct grounding/wiring/distance requirements.
Also... since many "active cables" do not have their own power, they can
only work to extend low power devices or devices with their own power.
{which is also where grounding becomes an issue}
Most models are actually mini hubs (thats what the chip/kink/bulky header on
one side of the cable does) but most users forget or are unaware of the max
4 hubs rule...
so if you have a Keyboard that has an extra port on it [which means that it
has a built in hub as well; examples are some sony USB keyboards are
detected as a four device hub, with 3 ports used], and use an active
extension cable. the usb mouse connected to that keyboard port is actually
on the "third" hub in the chain... which means that it can "break" if the
extenstion cable is not connected to the root hub...
most users do not realize the regulations on USB devices and so
manufacturers of the "regular" devices are the ones blamed when their device
fails to work when an extenstion cable is used... [which is why it seems
that some device manufacturers will only troubleshoot their devices if the
only items on the chain are their OWN hubs or connected to the root hubs]
...
----- Original Message -----
From: "Vojtech Pavlik" <[EMAIL PROTECTED]>
To: "Greg KH" <[EMAIL PROTECTED]>
Cc: <[EMAIL PROTECTED]>
Sent: Saturday, September 29, 2001 1:56 AM
Subject: Re: [linux-usb-devel] Active extenstion cables
> On Fri, Sep 28, 2001 at 04:51:46PM -0700, Greg KH wrote:
>
> > These devices are _very_ despised by the USB group, and are the main
> > reason that you have to sign a contract to use the USB 2.0 logo. They
> > also break the electrical USB spec quite badly, and cause problems, like
> > you're seeing :)
>
> And interestingly enough are becoming more and more widespread, even
> Belkin and Aten and others are now producing them. Btw, why would they
> break the electrical spec? If they do full repeating
> analog-digital-analog, it's quite OK to do so.
>
> My problem is, unfortunately, that I have three of these devices built
> into the walls of my home and can't replace them with true hubs easily.
>
> --
> Vojtech Pavlik
> SuSE Labs
>
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