The Difference Between a CAT3 & a CAT5 Cable

Two Ethernet cables

The difference between Category 3 and Category 5 cable is largely a difference of performance. The two standards established by the Telecommunications Association and the Electronics Industry Association both use the RJ-45 terminator, which causes them to look superficially similar.

Category 3 Cable

Category 3 was a standard used in the 1990s that defined how computer networking cable could be made. Cat3, as it is popularly known, requires that cables be made of four pairs of small, insulated copper wires. Each wire is twisted around its twin, and each pair twisted around the others. This twisting helps to protect the electronic signals passing through the cable from degrading. Cat3 can usually support speeds of up to 10 megabits per second. Cat3 was supplanted as the industry standard by Cat5.

Category 5 Cable

Category 5 cable, like its predecessor Cat3, uses 4 pairs of twisted copper wires to prevent external interference with the signals it transmits. One large difference between the two is the distance between twists. In Cat5, the distance between twists is defined according to prime numbers, which helps to reduce issues between wires. Cat5 was updated to Cat5e shortly after release, with added standards on latency. Cat5e cable supports up to 1000 megabits per second.

Considerations

In the networking environment of today, Category 3 cable is no longer sufficient for most users. 10 megabits per second is roughly equal to 2 megabytes per second, which is the measure most users are familiar with. Two megabytes per second may sound good, but no network will ever reach the theoretical maximum bandwidth, and performance will suffer as a result. Both standards use the same jack, Registered Jack 45, meaning that it is usually relatively easy to replace Cat3 with Cat5e. While some people are using Category 6 cables, Cat5e is still the defining business standard in 2010.

References

• Cisco: CCNA Sample Chapter on Cables
• European Network Systems Engineering: Sample Page from Cat5e's Standard