Cabling ?

may be its illy ques “10/100 baseT” Ethernet twisted pair has 8 wires in total .
1 = Transmit
2 = Transmit
3 = Receive
4 = Not used
5 = Not used
6 = Receive
7 = Not used
8 = Not used
Total 4 wires used 4 available for anything else??