RJ45 Interface

Posted on Mar 31, 2024 by

What Is RJ45 Interface?

RJ45 interface is considered the most common twisted-pair connector for Ethernet cables and networks.

  • "RJ" means "registered jack" — a standardized telecommunication network interface for connecting voice and data equipment to a service provided by a local exchange carrier or long-distance carrier.

  • "45" is the number of the interface standard.

Physically speaking, the connectors that registered jacks use are mainly the modular connector and 50-pin miniature ribbon connector types. RJ45 connector is an 8-position, 8-contact (8P8C) modular plug, and jack, applied for Ethernet-based local area networks (LAN). RJ45 cable plug is usually made of a plastic piece with eight pins on the port. Four of the pins are used for sending and receiving data, and the other four are used for other technologies or power networking devices.

How to Identify RJ45 Interface Color Code?

T568A vs T568B are the two common wiring schemes, which are used to terminate the twisted-pair cable onto the connector interface. The two standards define how the RJ45 pinouts arrange the individual eight wires when linking the RJ45 connector to a cable. These wiring layouts have their own color convention to follow for electrical compatibility. The T-568B wiring scheme is considered to be the more commonly used one. The differences between T568A vs T568B in color conventions are shown in the figure below.


With regard to the two standards, there are two different connectivity forms. If both ends of the patch cords are wired on the basis of one standard, it is a straight-through connection. If not, it is a crossover connection. 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, or switch available.

RJ45 Cable Types

Cables that terminated with RJ45 connectors on both ends called RJ45 Ethernet cables. Cat5, Cat6, and Cat7 cables are the most common RJ45 cables used in today's network connection.

Cat5 vs Cat5e

Category 5 was originally designed to transmit at 100 MHz frequencies, providing a rated line speed of 100 Mbit/s. Cat 5 uses two twisted pairs (four contacts) with a max range of 100 meters. A Cate5e specification was later introduced with tighter specifications and standards. The new standard also required new cables to include all four twisted pairs. Over short distances, under ideal signal conditions, and assuming they have four pairs, Cat5 and Cat5e patch cable are capable of transmitting at Gigabit Ethernet speeds. Gigabit Ethernet uses an optimized encoding scheme specifically intended for operation within these lower signal tolerances.

Cat6 vs Cat6a

Backward compatible with Cat5e, Category 6 has strict standards and significantly improved shielding. Cat6 cable was designed as the standard for Gigabit Ethernet, providing native speeds of up to 1000 Mbit/s over a frequency of 250 MHz. By reducing the maximum cable distance from 100 meters to 55 meters, 10 Gigabit Ethernet is supported. Cat6a doubles the frequency to 500 MHz while continuing to reduce noise interference with grounded foil shielding. These improvements remove the cable distance penalty when operating in 10 Gigabit Ethernet.

Cat 7

Operating at frequencies up to 600 MHz, Cat7 was designed specifically to support the rated speeds of 10 Gigabit Ethernet. In addition to the shielding introduced by Cat6e, this new specification provides individual shielding for each of the four twisted pairs. Cat7 has a maximum distance of 100 meters while maintaining backward compatibility with Cat5 and Cat6. Cat7a increases frequencies to 1000 MHz, providing an augmented specification capable of supporting future 40/100 Gigabit Ethernet speeds. The increase to 1000 MHz also allows for the transmittal of lower-frequency Cable TVstreams.

Cat 8

Cat8 network patch cable is the cost-effective solution for indoor data center applications, supporting up to 25/40GBase-T and 2000MHz within 30 meters of cable. And it is fully backward compatible with all the previous categories.

RJ45 Cable Applications

RJ45 connectors are the key part of Ethernet connectivity to transmit voice and data media. They were developed as much smaller and cheaper replacements to the older telephone installation methods of hardwired cords. The easy plug-n-play style reduces the difficulty of installation. Compared with RJ11, RJ45 is suitable for more applications, such as Ethernet networking, telecommunications, factory automation, and so on. It is frequently used for networking devices including Ethernet cables, modems, computers, laptops, printers, etc.

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