ANSI/EIA (American National Standards Institute/Electronic Industries
Association) Standard 568 is one of several standards that specify "categories"
(the singular is commonly referred to as "CAT") of twisted pair cabling
systems (wires, junctions, and connectors) in terms of the data rates that
they can sustain. The specifications describe the cable material as well
as the types of connectors and junction blocks to be used in order to conform
to a category. These categories are:
| Category | Maximum data rate | Usual application |
|---|---|---|
| CAT 1 | Less than 1 Mbps | analog voice (plain old telephone service)
Integrated Services Digital Network Basic Rate Interface in ISDN Doorbell wiring |
| CAT 2 | 4 Mbps | Mainly used in the IBM Cabling System for token ring networks |
| CAT 3 | 16 Mbps | Voice and data on 10Base-TEthernet |
| CAT 4 | 20 Mbps | Used in 16 Mbps
Token Ring
Otherwise not used much |
| CAT 5 | 100 Mbps | 100 Mbps TPDDI
155 Mbps asynchronous transfer mode |
CAT 5 is currently under consideration to be incorporated into the Gigabit Ethernet specification for short distance wiring. While longer connections using Gigabit Ethernet use optical fiber, the goal is to leverage the CAT 5 twisted-pair wiring most organizations already have in place for connections out to the desktop.
The two most popular specifications are CAT 3 and CAT 5. While the two
cables may look identical, CAT 3 is tested to a lower set of specifications
and can cause transmission errors if pushed to faster speeds. CAT 3 cabling
is near-end crosstalk-certified for only a 16 MHz signal, while CAT 5 cable
must pass a 100 MHz test.