Category 3 cable (aka Cat 3) is an unshielded twisted pair (UTP) cable designed to carry data up to 10 Mbit/s, with a possible bandwidth of 16 MHz.  Category 3 cable was used in computer networks in the early 1990′s.  Cat 3 is still currently used in two-line telephone systems.

Category 5 cable (aka Cat 5) includes 4 twisted pairs in a single cable jacket.  The maximum length for a Cat 5 cable segment is 100 meters.  Category 5 cable has been superseded by the Category 5e cable. Cat 5 cable is rated for tranmission frequencies up to 100 MHz.

Category 5e cable (aka Cat 5e) includes 4 twisted pairs in a single cable jacket.  The maximum length for a Cat 5e cable segment is 100 meters.  Cat 5e cable is rated for transmission frequencies up to 350 MHz (this frequency capability is still currently under debate).

Category 6 cable (aka Cat 6) includes 4 twisted pairs in a single cable jacket.  The maximum length for a Cat 6 cable segment is 100 meters.  Category 6 cable (Cat 6) is a cable standard for Gigabit Ethernet.  Cat 6 cable is rated for transmission frequencies up to 250 MHz.

Category 6a cable (aka Cat 6a) includes 4 twisted pairs in a single cable jacket.  The maximum length for a Cat 6a cable segment is 100 meters.  Category 6a cable (Cat 6a) is a cable standard for Gigabit Ethernet.  Cat 6a cable is rated for transmission frequencies up to 500 MHz.

Category 7 cable (aka Cat 7) includes 4 twisted pairs in a single cable jacket.  Shielding has been added for individual wire pairs and the cable as a whole.  The maximum length for a Cat 7 cable segment is 100 meters.  Category 7 cable (Cat 7) standards created to allow for 10 Gigabit Ethernet.  Cat 7 cable is rated for transmission frequencies up to 600 MHz.

Category 7a cable (aka Cat 7a) includes 4 twisted pairs in a single cable jacket.  Shielding has been added for individual wire pairs and the cable as a whole.  The maximum length for a Cat 7a cable segment is 100 meters.  Category 7a cable (Cat 7a) standards created to allow for 10 Gigabit Ethernet.  Cat 7a cable is rated for transmission frequencies up to 1,000 MHz.  Simulation testing results have shown that 40 Gigabit Ethernet is possible at 50 meters and 100 Gigabit Ethernet is possible at 15 meters with Category 7a cable.