What is RJ45 Cable? Pinout & Types (Patch, Crossover & more)

CAT cables, commonly known as RJ45 cables are used in LAN (Local Area Network) for internet or data transfer. They are available in various categories, like CAT5, CAT6, etc. And also have different types, like Straight cable (Patch cable), and Crossover cable.

In this article, we will discuss RJ45 cable in detail. We will also see different types of Ethernet cables and look at the speeds supported by different cable standards.

What is RJ45 Cable? (Ethernet cable)

RJ45 cable consists of 8 wires of different colors that connects to a connector head. One end of the cable connects to the port on your laptop, while the other end connects to a router or modem to transfer the signals.

What is RJ45 cable?
RJ45 cable

This standard is known as 8P8C (8-position 8-contact). The 8 cables are used as 4 pairs. This set of cables is shielded together as twisted pairs, which are known as twisted pair cables.

Note: The Ethernet require only two pairs of wire, i.e., Orange and Green for internet connection. The other two pairs, i.e., Blue and Brown are used as ISDN or phone connections. 

It enables multiple connections with a single connector due to which RJ45 was initially known as modular connectors. The connector comes with an orientation tab that helps in proper wiring.

Type of cables used in RJ45 connectors

RJ45 connector uses twisted-pair cables. These twisted pair cables are available in Unshielded Twisted Pair and Shielded Twisted Pair.

Unshielded Twisted Pair (UTP)

  • It consists of 4 pairs of color-coded wires that are twisted around each other. This is done to prevent electromagnetic interference and distortion of the signal.
  • It is used in home and office networks.

Shielded Twisted Pair (STP)

  • It is similar to a shielded twisted pair cable, but it has an extra layer of protection against electromagnetic interference.
  • It is used for industrial purposes.

Types of twisted-pair cable on the basis of wiring standards

Ethernet cable can be wired using two different wiring standards, i.e., 568A and 568B. The difference between these two standards lies in the order, in which pairs are arranged inside the cable. Based on this these standards, there are two types of twisted pair cable:

Straight Cable(Patch)

When the two ends of the ethernet cable are connected using the same standard (either 568A or 568B), it is called a Straight or Patch cable. It is generally used to connect two dissimilar devices together. For example a laptop to a modem.

RJ-45 Straight Cable Pinout

RJ-45 Straight cable pinout
RJ-45 Straight cable pinout

As visible in the figure above, both connectors at the ends of the cable have the same standard (here shown T568-B).

Crossover Cable

When the two ends of the ethernet cable are connected using opposite standards (one end 568A and the other end 568B), it is called a Crossover cable. It is generally used to connect two similar devices together. For example a laptop to another laptop.

RJ-45 Straight Cable Pinout

RJ-45 Crossover cable pinout
RJ-45 Crossover cable pinout

As visible in the figure above, both connectors at the ends of the cable have different standards. One side of the cable is connected in T568-B standard, while the other is connected in T568-A standard.

What are the different categories of twisted pair cables?

The five main categories used in twisted-pair are CAT3, CAT5, CAT6, CAT7, and CAT8. Out of these, CAT5 and CAT6 wires are commonly used with RJ45 connectors. The difference in the categories is the maximum speed they can handle without any interference. The table below gives the maximum speed provided by each category.

CategoryMaximum Speed
CATEGORY 3 (CAT3)10 Mbps
CATEGORY 5 (CAT5)100 Mbps
CATEGORY 5e (CAT5e)1 Gbps (Enhanced)
CATEGORY 6 (CAT6)1 Gbps (10 Gbps, if used with cable of length less than 100meters)
CATEGORY 6e (CAT6e)10 Gbps (Augmented)
CATEGORY 7 (CAT7)10 Gbps (Added shielding to wires)
CATEGORY 8 (CAT8)40 Gbps (Distance up to 30 meters)
Maximum Speed of Different Categories of Cables

Are RJ45 and CAT6 the same?

No, RJ45 and CAT6 are not the same. The RJ45 is a connector, while CAT6 (CATEGORY 6) is a model of twisted-pair cables. But, CAT cables are commonly referred to as RJ45 cables or Ethernet cables.

Applications of RJ45 cables

RJ45 cables are commonly used in Ethernet connections. Yet, they are useful for other applications also. For example:

  • Automation systems
  • Process control systems
  • Fabrication and assembly of Industrial robotic arms
  • Measurement systems
  • Quality Control
  • Voice Over Internet Protocol (VOIP) Devices
  • Internet of Things (IoT) Devices

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