Cat 3 cable, introduced in the early 90’s, is still used in some businesses where PBX phone systems and Voice over Internet Protocol (VoIP) installations still use the slower 10Base-T Ethernet installation. This cable uses two of the four twisted pair cables available giving speeds of 10 megabits per second (Mbs). Cat 3 saw a resurgence when the 100Base-T-4 standard was introduced. This standard, which trundles along at up to 100 mbps, uses all four pairs of wires within a Cat 3 cable allowing businesses that were wired for Cat 3 to retain their existing wiring offering an upgrade to the higher speeds. Cat 3 is still very popular as it is much less expensive than Cat 5 and higher standard cable.

How to wire your own cables

Cat 5 cable, introduced in the mid 90’s to replace the above Cat 3, uses the 10/100 Base-T network system and was deprecated in 2001 to be replaced by Cat 5e. Used on networks with speeds up to 100 Mbs.

Cat 5e, introduced in the late 90’s, has 24 gauge twisted pair wires producing a Gigabit network at distances up to 328 ft. This was introduced simply to enable 1000mbs networking (1 Gigabit) but both ends of the cable had to be attached to equipment that could handle the speed meaning your router AND the network card had to be able to run at 1Gbs. Otherwise the network dropped back to 100mbs if one or both pieces of equipment had that as its top speed.

Cat 6 cables came out only a few years after Cat 5e. This cable gave the ability to have a 10 Gigabit network. For much of the last decade (noughties) Cat 5e was used for workstations (client PC’s) while Cat 6 was used to run as a backbone from router to switches. However, the 10 Gigabit network on Cat 6 cables is limited to 164 ft. After that distance its ultimate speed is the same as Cat 5e (1 Gigabit). This cable has a tighter twist in the cables, which allows for two-way communication on each pair of wires, where Cat 5e does not allow this feature. Cat 5e cable has a tendency to have a higher delay and skew than Cat 6 cable meaning that even though both Cat5e and Cat 6 can do 1 Gigabit networks, Cat 5e may have a longer delay for the signal to get from one side to the other, giving the appearance it runs slower.

Cat 6a is thicker than Cat 6 which, in turn, is thicker than Cat 5 and, in part, is due to the extra-thick plastic around the wires themselves and to the tighter winding of the pairs creating more copper per inch. Cat 6a will do 10 Gbs networking for the full distance of Ethernet (328 ft.) also reducing the crosstalk among the pairs, which, in turn, further reduces the delay in the cables.