On Fri, 2003-07-25 at 02:19, Yehuda Drori wrote:
> ביום חמישי, 24 ביולי 2003, 17:13, Aviram Jenik כתב:
> > On Thursday 24 July 2003 16:45, Beni Cherniavsky wrote:
> >
> > <rant about non-crossed cables>
> >
> > > I recall that some new cards "autodetect polarity". Does this refer
> > > to polarity on each pair or also to Tx/Rx autodetection? Is there a
> > > chance that it will work with crossed cables anyway?
> >
> > I never heard of network cards that do that, but many switch-hubs (even
> > relatively cheap ones) are able to use crossed or non-crossed cables;
> > specifically - some D-Link ADSL router/hubs do that.
> >
> > > Is it safe to
> > > experiment of do I risk letting the smoke out?
> >
> > Completely safe. Connecting crossed cable instead of non-crossed will
> > simply not work, but it won't damage the equipment.
>
> yet another solution...
>
> I once bought sockets for RJ45 and connected them in a crossed manner..
>
> I used that when I had a need to extend a cable using two cables and in the
> same time to cross them over..
>
> <------------------> }=======x======{ <---------------->
> 1st cable crossing sec. 2nd cable
>
>
> this way you can re-cross the cables to be straight again..
>
>
> I think you can also find RJ45 extentions much the same as those used to
> extend phone lines and re-cross them to the same end..
>
> the prob is that you need a cable ( even a short one ) for each extended
> line...
>
> the wires need to be crossed are if I remember right..
>
> 1<--->3
> 2<--->6
>
> all the rest are kept straight
>
Actually all the rest don't matter. you can just use a 4 wire cable to
save on cable thickness/cost.
Just make sure that unless its a very short cable, and even there its
still preferable, to use twisted pair cable (each pair of wires are
twisted all along the cable) preferably cat5, and to use one twisted
pair for direction, i.e one for
1<--->3
2<--->6
and the second for
3<--->1
6<--->2
(the conection is semetric). There are actual standard color codes but
you don't need to head then for you personal cables.
The twisting is important to handle environment radiation noise. Since
the signal isn't measured directly as the voltage on each wire but as
the voltage difference between the wires, thus if there is an
elecromagnetic disturbance, due to the twist in the wires it would
effect them both the same and won't cause errors. Each computer
transmits on the 1,2 pair and recieves on the 3,6 pair.
On very long cables this also helps handle signal instability due to
signal decay.
The idea is that we get a bad signal, but we know how its degraded and
thus are able to recostruct the intended signal.
=================================================================
To unsubscribe, send mail to [EMAIL PROTECTED] with
the word "unsubscribe" in the message body, e.g., run the command
echo unsubscribe | mail [EMAIL PROTECTED]
