Category 3: cable is designed for voice and data communication. It is a 4-pair unshielded
twisted pair cable that will support data transmission up to 10Mbps (Mega Bits per Second). 10Mbps data transmission is the well known Ethernet standard. This is also referred to as 10Base-T.
Category 5: cable is designed for data communication, but can also be used for voice. It also
is a 4-pair unshielded twisted pair cable that will support data transmission up to 100Mbps. Data communications over category 5 cable at 100 Mbps comes in two flavors. The most popular is
referred to as Fast Ethernet and is also known as 100Base-T. A less popular version is referred to as 100VG-Anylan
Category 5e: Also known as Enhanced category 5, this cable is somewhat higher in
performance than the category 5 cable above. In order to install a category 5e system, the jacks at the workstation locations and the patch panel in the equipment room must also be rated at
category 5e. Currently, manufacturers have discontinued making category 5 cable as the industry moves toward the higher performance of category 6. Category 5e is now the minimum recognized
performance level for unshielded cable used for data communication.
Category 6: as well as category 7 are the newest specifications for high performance cabling.
Category 6 is to be specified to 250Mhz and category 7 is to be specified to 600Mhz. These advanced cables are suited for supporting Gigabit Ethernet, also known as 1000Base-T. Of
course, this high performance also carries with it a much higher cost. Unless there is a specific need or requirement for this higher performance cable, category 5e is still a viable solution for the
majority of customer installations. Ratification of the associated standards for category 6 and 7 is not predicted for several months.
Modular Jack Styles
The 6 position jack is commonly used for voice systems. The 6 position modified jack is also
referred to as a Modified Modular Jack, or MMJ. It was designed by Digital Equipment Corporation® (DEC) along with the modified modular plug (MMP) to eliminate the possibility of
connecting DEC data equipment to voice lines and vice versa.
The 8 position jack is commonly used for data installations using category 5 type cable. The
modified version of the 8 position jack was designed with a matching "keyed" plug that would hopefully keep someone from plugging this keyed plug into the wrong modular outlet. This type of
jack and plug is rarely used.
The 6-position modular jack is commonly referred to as an RJ11. Using these terms can
sometimes lead to confusion since the RJ designations actually refer to very specific wiring configurations contained in the Universal Service Order Code (USOC) book. The designation “RJ” means
Registered Jack. Each of these basic jack styles can be wired for different RJ configurations. For example, the 6-position jack can be wired as an RJ11C (1-pair), RJ14C (2-pair), or
RJ25C (3-pair) configuration.
The same holds true of the 8 position jacks. The 8-position modular outlets are commonly
and incorrectly referred to as RJ45. An 8-position jack can be wired for configurations such as RJ61C (4-pair) and RJ48C. The keyed 8-position jack can be wired for RJ45S, RJ46S, and RJ47S.
Even though it is technically incorrect, when most people refer to an RJ45 jack, they are referring
either to a jack or plug that has 8 wires contained within an 8 position footprint, (8w x 8p).