Q & A on 10BaseT Termination and Cabling Q: Why does the twisted pair standard specify RJ-45 termination, a 4-pair wiring connector, when the Ethernet standard only uses 2 pairs for Tx and Rx? A: The 8-pin connectors provide additional wires that can be used either as backup or for additional signals (some higher speed networks use two pairs to transmit data at a higher rate). As an aside: one engineer told ne that he thought the choice of RJ-45 jacks instea of RJ-11 jacks was important to making 10BASE-T a success. It seems that his company had used RJ-11 jacks on an earlier piece of data communication, and they were plauged with complaints from customers who had tried to plug in telephones... :-) Q: Likewise, why is CAT-5 so pervasive when the networking market is so price driven? It would seem that a cable with only 2-pairs would be less expensive; i.e., more widely used. A: The higher price of category 5 arises because the cable is manufactured to higher standards. In particular, the way the wires are twisted pairs and the isulation guarantee that the cable is less susceptible noise and crosstalk. Although lower categories (e.g., cat 3) are adequate for telephone connections, they do not provide as much shielding against interference.