Category 3 Cabling

Category 3 cabling is the third-lowest grade of unshielded twisted-pair (UTP) cabling.

What is Category 3 cabling?

Category 3 Cabling is the third-lowest grade of unshielded twisted-pair (UTP) cabling. Category 3 cabling was designed to support digital voice and data communication at speeds up to 10 Mbps.

Category 3 Cabling
Category 3 Cabling

It uses 24-gauge copper wires in a configuration of four twisted-pairs enclosed in a protective insulating sheath. Category 3 cabling is the lowest grade of UTP cabling that can support standard 10BaseT types of Ethernet networks and was often used for legacy 4-Mbps Token Ring installations

Category 3 cabling still has an installed base in older buildings where it is often cheaper to use the existing cabling than to upgrade to newer grades.

Installing higher-grade cabling for backbone cabling in vertical rises and elevator shafts can extend the life of work areas that still use category 3 cabling. However, if greater speeds are required at users’ workstations, the best solution is to rewire the work areas using category 6 cabling.

Category 3 Cabling Characteristics

The following table summarizes the electrical characteristics of category 3 cabling at different frequencies, which correspond to different data transmission speeds. Note that attenuation increases with frequency, while near-end crosstalk (NEXT) decreases.

CharacteristicValue at 10 MHzValue at 16 MHz
Attenuation27 decibels/1000 feet36 decibels/1000 feet
NEXT26 decibels/1000 feet23 decibels/1000 feet
Resistance28.6 ohms/1000 feet28.6 ohms/1000 feet
Impedance100 ohms (± 15%)100 ohms (± 15%)
Capacitance18 pF/feet18 pF/feet

Source: ANSI-TIA-EIA 568-B – Commercial Building Telecommunications Cabling Standard