ethernet cabling FREE cabling and networking Helpdesk
 Question by Cecilia Anguita posted 20 Jul 2000
 ethernet cabling
We have an 10BaseT network. Each office is wired with one cable and two ports per cable. I know ethernet only uses 4 of the 8 wires to work. How does the speed work on this? Do we have less speed because we divide the cable in 2 ports?
 Answer by Roman Kitaev posted 21 Jul 2000
Hi, Cecilia!

No, you don't have less speed if you divide the 4-pair cable in 2 ports. If you have 10 Mbit network, you will have 10 Mbit on non-split and split cables without any difference.

The reason for splitting the 4-pair cable is simple:

As you mentioned, ethernet (10Base-T and 100Base-T) uses only 4 wires (actually, pair 2 and 3 from the 4-pair cable). That means that we can use pair 1 and pair 4 for something else. The usual procedure (although not a recommended one, the recommended solution is to use dedicated 4-pair cable for each port) is to use pair 1 for telephone.

That means that you have two outlets and pair 1 connects to the first outlet and the outlet is used for voice, pairs 2 and 3 connect to the second outlet and the outlet is used for data.

Sometimes, the cable is split like this: pairs 2 and 3 connect to the fist outlet, pairs 1 and 4 connect to the second outlet. In this case, both outlets are used for data.

Hope I answered all your questions.

Best regards,
Roman Kitaev, RCDD

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