What Is the Difference Between an RJ45 and RJ48?

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What Is the Difference Between an RJ45 and RJ48?
The RJ45 and RJ48 connectors look exactly the same. (Jupiterimages/Polka Dot/Getty Images)

The RJ45 and RJ48 jacks are two types of cable connectors for networks. They both use the same shaped plug, and so look identical. However, they connect to different types of cable with different wiring plans and so have different identification numbers.

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Registered Jack

Registered Jacks are a series of telephone terminal wiring plans codified by the US Federal Communications Commission. There is confusion about whether the code applies to the plug or the socket. In fact, the code applies to the wiring scheme within the plug and the socket. It does not refer to the design of the plug. The "RJ" in RJ45 and RJ48 is an abbreviation of "Registered Jack" and is used in the name of all registered jacks under the FCC scheme.


The RJ45 code applies to an eight pin, two contact design implemented for phone wiring. However, this format is rarely used for telephone. The Ethernet connectors recommended for network cabling look the same as the RJ45 plug. However, it is incorrect to apply this code to network jacks as they have eight pins and eight contacts and a different wiring plan. Nonetheless, everyone refers to the Ethernet jack as an RJ45.


The RJ48 standard is implemented exactly as per the FCC specifications. It uses the same plug as the RJ45, it also connects to eight wire structured cable the same as the Ethernet version of the RJ45.


Comparing the FCC RJ45 standard and RJ48 standard, the differences are clear. RJ45 connects two wires and the RJ48 connects eight. The RJ45 connects to Unshielded Twisted Pair cable and the RJ48 connects to eight wired Shielded Twisted Pair Cable. RJ45 is a specification for a telephone connector, RJ48 is a connector for a data cable.


A closer comparison is more meaningful between the FCC RJ48 and the Ethernet RJ45 jack, as both are meant to connect data cable. Both have eight pins and eight contacts, both connect to structured eight wire twisted pair cable. However, RJ45 terminates Unshielded Twisted Pair and RJ48 terminates Shielded Twisted Pair.


The effective difference the cable type creates is that of environment. The RJ45 with Unshielded Twisted Pair is ideal for short lengths of cable in indoor, protected office environments. It's lack of shielding makes it cheap and because of this is has become the most widely used cable for private networks, or LANs. Shielded Twisted Pair, terminated by RJ48 connectors is more robust and has greater protection against environmental interference. It can carry data further and in harsher environments, like outdoor or where there is likely to be more radio frequency interference or electromagnetic interference. RJ48 is used to terminate T1 data cables, which extend over further distances than LAN cables.

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