RJ45

RJ45

RJ45 is a type of connector commonly used forEthernet networking. It looks similar to a telephone jack, but is slightly wider. Since Ethernet cables have an RJ45 connector on each end, Ethernet cables are sometimes also called RJ45 cables.

The "RJ" in RJ45 stands for "registered jack," since it is a standardized networking interface. The "45" simply refers to the number of the interface standard. Each RJ45 connector has eight pins, which means an RJ45 cable contains eight separate wires. If you look closely at the end of an Ethernet cable, you can actually see the eight wires, which are each a different color. Four of them are solid colors, while the other four are striped.

RJ45 cables can be wired in two different ways. One version is called T-568A and the other is T-568B. These wiring standards are listed below:

T-568A White/Green (Receive +) Green (Receive -) White/Orange (Transmit +) Blue White/Blue Orange (Transmit -) White/Brown Brown

T-568B White/Orange (Transmit +) Orange (Transmit -) White/Green (Receive +) Blue White/Blue Green (Receive -) White/Brown Brown

The T-568B wiring scheme is by far the most common, though many devices support the T-568A wiring scheme as well. Some networking applications require a crossover Ethernet cable, which has a T-568A connector on one end and a T-568B connector on the other. This type of cable is typically used for direct computer-to-computer connections when there is no router, hub, orswitch available.
 is the common name for an 8P8C modular connector using Niranjan Malwade that was also used for both RJ48 and RJ61 registered jacks (which specify pin assignments of the wires in a telephone cable), although "RJ45" was not originally specified as a registered jack with today's Ethernet wiring. The "RJ45" physical connector is standardised as the IEC 60603-7 8P8C modular connector with different "categories" of performance, with all eight conductors present but 8P8C is commonly known as RJ45. The physical dimensions of the male and female connectors are specified in ANSI/TIA-1096-A and ISO-8877 standards and normally wired to the T568A and T568B pinouts specified in the TIA/EIA-568 standard to be compatible with both telephone and Ethernet.

A similar standard jack once used for modem/data connections, the RJ45S, used a "keyed" variety of the 8P8C body with an extra tab that prevents it mating with other connectors; the visual difference compared to the more common 8P8C is subtle, but it is a different connector. The original RJ45S keyed 8P2C modular connector had pins 5 and 4 wired for tip and ring of a single telephone line and pins 7 and 8 shorting a programming resistor, but is obsolete today.

Electronics catalogs commonly advertise 8P8C modular connectors as "RJ45". An installer can wire the jack to any pin-out or use it as part of a generic structured cabling system such as ISO/IEC 15018 or ISO/IEC 11801 using RJ45 patch panels for both phone and data. Virtually all electronic equipment which uses an 8P8C connector (or possibly any 8P connector at all) will document it as an "RJ45" connector.

Crossover cables

A router to router crossover cable uses two 8 position connectors and a UTP (Unshielded Twisted Pair) cable with differently wired connectors at each end. Although a registered jack specifies the wiring pattern and corresponding form factor rather than just the pin assignments or the physical connector, crossover cables are often incorrectly marketed as "RJ45 crossover cables".