RJ45 is a cable connector, a standard network plug and socket that is often referred to as an Ethernet jack. The most common form of network cable is Unshielded Twisted Pair. The UTP cable is manufactured following standards dictating the grade of cable. These standards categorise the cable as Cat 5 or Cat 6. Cat 5 or Cat 6 UTP cable is terminated by RJ45 connectors.
Unshielded Twisted Pair
UTP cable contains eight wires laid out as four pairs. Each pair represents the forward and negative path of a complete circuit. The two wires in each pair are twisted around each other for the length of the cable. Twisting the two wires together creates an inductor, which cancels up interference from background magnetic radiation. To prevent each pair interfering with each other each is wound at a different rate. The tighter the winding of the pairs, the greater the protection and the greater the cost. The difference between Cat 5 and Cat 6 UTP cable is that Cat 6 is wound tighter.
The standard Ethernet connector used for UTP cable is referred to as RJ45, although it does not officially conform to the RJ45 standard. RJ stands for "Registered Jack." The U.S. Federal Communication Commission standardised telephone jacks into categories that define their wiring plan. The RJ45 specification includes a connector with eight pins and two contacts. The eight pin layout is ideal for Ethernet connections because UTP cable contains eight wires. However, the Ethernet implementation uses a connector that looks like the RJ45 plug, but, in fact, contains eight contacts, making it different than the RJ45 standard.
As the main difference between Cat 5 and Cat 6 cable is the rate of winding, the connection between the cable and the connectors at each end is no different. In a standard network implementation four of the eight wires offer a transmit and receive path for a computer to communicate with networking hardware, like a hub or a switch. The two transmit wires are a positive and a negative wire twisted together as are the two wires of the receive path. Computers send data on the transmit wires and listen on the receive wires.
The basic difference between Cat 5 and Cat 6 RJ45 cable is the rate of winding of the constituent twisted pairs. This one physical difference brings a number of performance differences. Primarily, a Cat 6 UTP cable is able to carry data faster and over greater distance than Cat 5 UTP cable.