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I have been curious on this for a while since there are some people who use a modified CAT5e cable with a switch to disconnect data sending without actually disconnecting the whole internet connection.

For the above statement: I will explain further: they cut the green wire inside the CAT5e cable, attach a switch and from there they can just simply switch on and off without actually disconnecting.

Can someone explain what colors correspond to what functions in Cat5e?

If so I would be very appreciative. Thank you very much!

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up vote 1 down vote accepted

1. TX+: Simplex (Transmit), positive
2. TX-: Simplex (Transmit), negative
3. RX+: Simplex (Receive), positive
6. RX-: Simplex (Receive), negative


  1. TX_D1+: Simplex (Transmit), positive
  2. TX_D1-: Simplex (Transmit), negative
  3. RX_D2+: Simplex (Receive), positive
  4. RX_D2-: Simplex (Receive), negative
  5. BI_D3+: Duplex channel 1, positive
  6. BI_D3-: Duplex channel 1, negative
  7. BI_D4+: Duplex channel 2, positive
  8. BI_D4-: Duplex channel 2, negative
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interesting, that's quite clear enough with the picture from Denis below... :) – DucDigital Nov 26 '09 at 4:56

It depends on the wiring scheme. This table is copied from the Wikipedia page for TIA/EIA-568-B:

alt text

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