In ethernet what is CAT5 cable and RJ45?

Question

I heard people talk about 'CAT5' and 'RJ45'. Do these only apply to an ethernet LAN?
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What do each other these two terms mean? How are they related to twisted pair copper cable and fiber optic cables?
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The usual home analog telephone also has a connector similar to RJ45. What is it called? And how is it different from a LAN connector?
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What are some other similar terms that are often used?

Answer 1

Cat 5 (Category 5 cable) is the type of wire/cable used for Ethernet (100base-T)



It is made from 4 pairs of copper wire (8 all together) that are twisted together. The twisting helps protect the data from interference and noise. Cat 5 cables can be up to 100 meters long



RJ-45 is the type of plug.



Cat 5 is twisted copper cable (not fiber optic). The RJ-45 connectors are used to plug the cable into the computer/router/etc.



Analog telephones use RJ-11 connections which look like smaller versions of RJ-45



Wikipedia has some good pictures of all this:

http://en.wikipedia.org/wiki/Category_5_cable





Related terms:

Cat 5e - used for Gigabit ethernet (1000base-T)



Shielded/Unshielded - most cat 5 cables are unshielded. Shielded cables have a grounded foil wrapper around the twisted wire pairs that protects the data from "noise" (electromagnetic interference)



Full Duplex - This means that Ethernet connections can both send and receive data at the same time (think of a telephone vs. a walkie-talkie. the walkie-talkie is only Half Duplex)



Rx/Tx - Inside of Cat5 cable, two wires are designated to receive data (the Rx wires) and two are designated to send (transmit) data (Tx wires)



Crossover Cable - this type of cable is used to connect two computers/devices without using a router or switch. The crossover cable connects one device's Rx lines with the other device's Tx lines (Basically, the Rx and Tx lines are switched on one of the RJ45 connectors)



Network Interface Card (NIC) - this is the component that allows your computer to connect to the Ethernet network.

Answer 2

Cat(egory) 5 is a rating of twisted pair wiring. There are also other categories, such as Cat 5e and Cat 6. The RJ45 is the plastic connector on the end. There are other uses for the RJ45 connection - sometimes to a console interface or even in "newer" token ring networks ("newer" being a relative term since token ring is all but extinct). Neither Cat5 (or 5e or 6) or RJ45 connectors are used in fiber optics.



The telephone connector is an RJ11 connector. It's different both in size and in the number of wires it accomodates. The RJ45 accepts up to 8 wires (4 pairs); the RJ11 accepts 6 wires (3 pairs).

Answer 3

RJ45 is the type of connector on the end.

Cat 5 refers to the cable itself, it is a specification that the cable meets regarding its construction and performance.



Fibre optic cables carry light, copper cables carry electricity. They are both methods of transferring data. Twisted pair refers to the way the cables are arranged - they are twisted together in pairs to reduce interference and improve the signal quality.



The telephone connector is RJ11. It differs from the RJ45 connector in that it has a different number of contacts, 6 compared to 8.

Answer 4

What Is Rj45