8 pin RJ45 (8P8C) female connector
This is the 8 pin RJ45 (8P8C) female connector
A modular connector (i.e. 8P8C RJ45) is an electrical connector that was originally designed for use in telephone wiring, but has since been used for many other purposes. Probably the best known applications of modular connectors is Ethernet.
Modular connectors were originally used in the Registration Interface system, mandated by FCC in 1976 in which they became known as Registered Jacks. The registered jack specifications define the wiring patterns of the jacks, not the physical dimensions or geometry of the connectors of either gender. These latter aspects are covered by ISO standard 8877. TIA/EIA-568 is a standard for data circuits wired on modular connectors.
The 8 position 8 contact (8P8C) connector is a modular connector commonly used to terminate twisted pair and multi-conductor flat cable. These connectors are commonly used for Ethernet over twisted pair, registered jacks and other telephone applications, RS-232 serial using the EIA/TIA-561 and Yost standards, and other applications involving unshielded twisted pair, shielded twisted pair, and multi-conductor flat cable.
An RJ45 8P8C modular connection has two paired components: the male plug and the female jack, each with eight equally-spaced conductors. On the plug, these conductors are flat contacts positioned parallel with the connector body. Inside the jack, the contacts are suspended diagonally toward the insertion interface. When an 8P8C plug is mated with an 8P8C jack, the contacts meet and create an electrical connection. Spring tension in the jack's contacts ensures a good interface with the plug and allows for slight travel during insertion and removal.
Although commonly referred to as an RJ45 in the context of Ethernet and category 5 cables, it is incorrect to refer to a generic 8P8C connector as an RJ45. A telephone-system-standard RJ45 plug has a key which excludes insertion in an un-keyed 8P8C socket. The registered jack (RJ) standard specifies a different mechanical interface and wiring scheme for an RJ45S from TIA/EIA-568-B which is often used for modular connectors used in Ethernet and telephone applications. 8P8C modular plugs and jacks look very similar to the plugs and jacks used for FCC's registered jack RJ45 variants, although the RJ45S is not compatible with 8P8C modular connectors.