Craig White wrote:
I could have sworn that the CAT 3 cable I used for networking was 4 pair, and not 2 pair. I can remember some 2 pair cable use for POT connections, but every networking application was 4 pair. Now, both 10BaseT and 100BaseTx only use 2 pair, but the cable is normally 4 pair. Now, there is a difference a physical difference between CAT 3 and CAT 5, but it has more to do with how the pairs are twisted together then the number of wires. The number of wists/inch, and the relationship between the number of twists in each pair change the electrical characteristics of the cable. (Each pair has a different twist rate.) I think how the pairs are twisted together in the cable is also specified.it seems that you are ignoring the reality that Cat 3 cables (10Base-T) are physically different than Cat 5 cables. Cat 3 cables needed only 4 wires and Cat 5 cables needed 8, thus expecting a Cat 3 cable to work properly at 100Base-T is not realistic at all. This of course ignores the different twisting requirements for shielding.
What gets interesting is that with the proper test equipment, you can detect the different twist rate of the cable, the total length, any connections in the run, and even sharp bends in the cable. You can also tell the difference between CAT 3 and CAT 5 cable. I have to admit that the equipment that does this is a lot more expensive then a simple pair tester, but when you have to certify an installation, it is necessary. (cable length, noise level, crosstalk, etc...)
Mikkel -- Do not meddle in the affairs of dragons, for thou art crunchy and taste good with Ketchup!
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