RJ45

RJ45 refers to the widely used 8-position, 8-conductor modular connector and plug used for Ethernet over twisted-pair copper cabling. Although commonly called RJ45, the connector is technically an 8P8C (eight positions, eight contacts) modular connector, and RJ-45 is the registered jack designation widely used in Ethernet terminology. The plug mates with RJ45 sockets on network devices such as computers, switches, routers, and patch panels, and is standard with Category 5e, Category 6, and higher cables.

Wiring and pinout are defined by the TIA/EIA-568 standards, with two common end configurations: T568A and T568B. In T568B, the pin order is 1 white/orange, 2 orange, 3 white/green, 4 blue, 5 white/blue, 6 green, 7 white/brown, 8 brown. In T568A, the order is 1 white/green, 2 green, 3 white/orange, 4 blue, 5 white/blue, 6 orange, 7 white/brown, 8 brown. Most commercial runs use 568B on both ends; a cable with different standards on each end is a crossover cable. Modern equipment often supports auto-MDI/MDIX, reducing the need for crossover cables.

Performance and usage: the RJ45 connector supports Ethernet speeds such as 10BASE-T, 100BASE-TX, and 1000BASE-T, with gigabit performance typically achieved on Cat5e or Cat6 cables. Higher-category cables (Cat6a, Cat7) enable 10 Gbps and beyond while using the same 8P8C plug. RJ45 connectors can also support Power over Ethernet (PoE), delivering power to endpoints like IP cameras and VoIP phones over the data pairs.

Variants and considerations: RJ45 can be used with unshielded (UTP) or shielded (STP) cabling, and jacks may be shielded or unshielded. Proper termination, cable quality, and shielding influence reliability and performance.