Category 5 cabling

Category 5 cabling is a level 5 grade of unshielded twisted-pair (UTP) cabling.

What is Category 5 cabling?

The highest and most commonly used grade of unshielded twisted-pair (UTP) cabling in networking today. Category 5 cabling was designed to support digital voice and data communication at speeds up to 100 Mbps. It uses 22-gauge or 24-gauge copper wires in a configuration of four twisted-pairs enclosed in a protective insulating sheath. Category 5 cabling is the standard grade of UTP cabling for networks such as:

  • The standard 10BaseT variety of Ethernet
  • Fast Ethernet networks of the 100BaseTX variety

Category 5 cabling is always recommended for new installations of premise cabling and for upgrading existing premise wiring for higher-speed networks, because of its superior electrical characteristics. It is the highest grade of UTP cabling currently recognized by the Electronic Industries Alliance (EIA) and Telecommunications Industry Association (TIA), although proposals there have made for higher category 6 and category 7 grades. Many vendors offer an enhanced category 5 cabling grade with electrical characteristics exceeding those of standard category 5. Enhanced category 5 cabling supports data transmission up to frequencies of 350 MHz, and new standards are under development to allow even higher data transmission frequencies.

NOTE

The following table summarizes the electrical characteristics of category 5 cabling at different frequencies, which correspond to different data transmission speeds. Note that attenuation increases with frequency, while near-end crosstalk (NEXT) decreases.

Category 5 Cabling Characteristics
Characteristic Value at 10 MHz Value at 100 MHz
Attenuation
20 decibels/1000 feet
67 decibels/1000 feet
NEXT
47 decibels/1000 feet
32 decibels/1000 feet
Resistance
28.6 ohms/1000 feet
28.6 ohms/1000 feet
Impedance
100 ohms (± 15%)
100 ohms (± 15%)
Capacitance
18 pF/ft.
18 pF/ft.
TIP

Category 5 cabling is usually referred to simply as “CAT5.” UTP cables using CAT5 should be no more than 90 meters in length for typical Ethernet and Fast Ethernet installations, and patch cords should be no longer than 10 meters.