A Category 3 cable (Cat 3 cable) is a type of unshielded twisted pair (UTP) cable that is used for voice and data communications in computer and telecommunication networks. It is an Ethernet copper cable defined by the Electronics Industry Alliance (EIA) and Telecommunication Industry Association (TIA).
It was also used for Ethernet distribution (10/100 Mb/sec) until around Y2K, when CAT5(e) came to town and allowed 1Gb/sec. (b=bits)
-Dennis
The whole US telephone network is built on unshielded, untwisted pair. Really no need, it's all 600ohm balanced with a good CMRR.
I laugh when people talk about crosstalk because large feeders into CO's are thousands of pairs and it's not a problem. Old phone guys are great at chasing bad pairs with their Simpson's worn around the neck.
In fact the only shielded cable is call ABAM, and it's 75ohm multicore used for DS-3 (45Mbps) and some special TV circuits. Even radio station broadcast specials went on copper. It was "conditioned" by using repeaters and prescription equalizers (fixed EQ programmed with DIP switches).