MIKE FARRILL wrote in a message to DAVE SHINER:
DS> Basically the difference between the Cat "x" is the amount of twists
DS> foot(there's more to the specs if you REALLY want to know).  The more
DS> twists, the higher the noise rejection of the cable. Cat 3 is
DS> adequate for 10mps Ethernet, while Cat 5 is required for 100mps
DS> Ethernet. Shielding will attenuate the the signal when used in a
DS> high speed network, that's why you use UTP.
 MF> Attenuate, what does that mean specifically?
Visualize the center conductor and the shield as being two plates of a 
capacitor.  This capacitance will allow a high frequency signal to see a low 
impedance path to ground.
DS> It's easy enough to avoid noisy things in a house.  Try to route 
DS> your cables away from electric motors, fluorescent lights, speakers 
DS> etc.
 MF> If I got a shielded cable, would I still have to do that?
It would be a good idea.  A shielded cable is not 100% impervious to outside 
signals.  Depending on the shield construction (braid, foil, whatever), the 
coverage can drop well below 100%.
Regards,
       David
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