Cat 4 or Category 4 Cabling is the fourth-lowest grade of unshielded twisted-pair (UTP) cabling. Category 4 cabling was designed to support digital voice and data communication at speeds up to 16 Mbps.
It uses 22-gauge or 24-gauge copper wires in a configuration of four twisted-pairs enclosed in a protective insulating sheath. Category 4 cabling can support standard 10BaseT types of Ethernet networks. It was also commonly used in older 16-Mbps Token Ring installations.
Category 4 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 4 cabling. However, if greater speeds are required at users’ workstations, the best solution is to rewire the work areas using category 6 cabling.
Category 4 Cabling Characteristics
The following table summarizes the electrical characteristics of category 4 cabling at different frequencies, which correspond to different data transmission speeds. Note that attenuation increases with frequency, while near-end crosstalk (NEXT) decreases.
|Characteristic||Value at 10 MHz||Value at 20 MHz|
|Attenuation||20 decibels/1000 feet||31 decibels/1000 feet|
|NEXT||41 decibels/1000 feet||36 decibels/1000 feet|
|Resistance||28.6 ohms/1000 feet||28.6 ohms/1000 feet|
|Impedance||100 ohms (± 15%)||100 ohms (± 15%)|
|Capacitance||18 pF/feet||18 pF/feet|
Source: ANSI-TIA-EIA 568-B – Commercial Building Telecommunications Cabling Standard