Standard for Ethernet cables is established in 1985. Each network wire category has different specifications as far as shielding from electromagnetic interference, data transmission speed, and the possible bandwidth frequency range required to achieve that speed. Category of network wire is printed on the cable’s sheath, so there can be no doubt for the type of cable being used.
Category 3 is oldest form of Ethernet cable still in use today. It is an unshielded twisted pair (UTP) cable that is capable of carrying 10 megabits per second (Mbps) of data or voice transmissions. Its maximum possible bandwidth is 16 MHz. It can be seen in use in two-line telephone systems and older 10BASE-T Ethernet installations.
Category 5 is the successor to the earlier Category 3. It is a UTP cable, but it is able to carry data at a higher transfer rate. Cat 5 network wires can support either 10 Mbps or 100 Mbps speeds. This category has been superseded by the newer Category 5e cables.
Category 5e is an enhanced version of Cat 5 network wire. This category works for 10/100 Mbps and 1000 Mbps (Gigabit) Ethernet, and it has become the most widely used category of Ethernet cable. Both Cat 5 and Cat 5e cables contain four twisted pairs of wires, but Cat 5 only utilizes two of these pairs for Fast Ethernet, while Cat 5e uses all four, enabling Gigabit Ethernet speeds. Maximum bandwidth of Cat5e is 100 MHz.
Category 6 network wire is certified to handle Gigabit Ethernet with a bandwidth of up to 250 MHz. Cat 6 cables have several improvements, including better insulation and thinner wires, that provide a higher signal-to-noise ratio, and are better suited for environments in which there may be higher electromagnetic interference. Some Cat 6 cables are available in shielded twisted pair (STP) forms or UTP forms.
Category 6a allows 10,000 Mbps data transmission rates and its maximum bandwidth is 500 MHz. Category 6a cables are usually available in STP form, and must have specialized connectors that ground network wire.
Category 7 is a fully shielded network wire that supports speeds of up to 10 Gbps (10,000 Mbps) and bandwidths of up to 600 Mhz. Cat 7 cables consist of a screened, shielded twisted pair (SSTP) of wires. Each of the shielding layers must be grounded, or else performance may be reduced to the point that there will be no improvement over Cat 6.
Overview of the different Ethernet categories