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Ethernet is a common type of wired network.  An Ethernet cable has an end which looks a lot like a phone cable, only bigger.  Phone cables may have 2, 4 or 6 contacts in them while Ethernet cables always have 8.  Because of this an Ethrenet cable end is slightly bigger than a phone cable end.  In the image below the Ethernet end is on the left and the telephone end is on the right.  Note that while there are 4 gold-plated pins in the gold end there are 2 empty slots, one on either side, for 2 more.  Ethernet cable almost always has all 8 slots filled with pins, though some cheaper premade cable may not include pins for the brown and white with a brown stripe wires.  These wires are used only for Power Over Ethernet (POE), a technology where the device is powered by the switch instead of having its own separate power cord.  This is not common for home use.

Ethernet-Phone

The difference between the two is pretty clear when they are side by side.  An Ethernet cable will not fit into a phone jack.  However, a phone cable will fit into an Ethernet port, but will do nothing.

There are a few things to note when choosing Ethernet cable.

The first thing, mentioned above, is POE or Power Over Ethernet.  The brown and white with a brown stripe wires are normally not used in Ethernet cables, but they are when the device to be connected gets not only its network signal, but also its power from the switch.  This isn't very common in home use.  Most things home users would connect, such as printer and computer, use too much power to be able to power them over these tiny wires.  This is more common for things like network connected cameras.  Most home users will likely never see POE connections.

The next thing to consider is the category of cable.  The cable shown above is Category 5, often abbreviated CAT5.  All CAT5 cable these days is actually CAT5E, which is an improvement over regular CAT5 allowing transfer speeds up to one GB (Gigabit).  Older CAT5 Ethernet cables are usually flat, like telephone cables, only wider.  Newer CAT5E cables are round.  The wires are twisted inside the casing in a way that reduces interference.  Most users today are unlikely to ever see the older CAT5 cable.  There is also CAT6 cable, capable of speeds up to 10GB, however routers and switches capable of those speeds are not common.  CAT5E cable is the standard and is sufficient for most use.  Any user who would benefit from CAT6 cable likely has no need for the information on this page.

Next, CAT5E cable comes in 2 types, shielded and unshielded.  Your instinct would be to get the better, more expensive shielded cable, but your instinct is almost certainly wrong.  Shielded cable only works if you are using ends specifically designed to make it work.  The end pictured above is not such an end.  It is clear.  The ends for shielded Ethernet cable have a silvery hue to them.  If you do not use the silver, shielded ends with your cable the shielding isn't working.  Shielded cable also only works if the equipment on both ends also has the shielding ability built in.  The shielding wrapped around the wires is electrically connected to the ends, which in turn is electrically connected to ground through the devices on both ends.  That is important.  The device on BOTH ENDS must support shielded cable.  If you have shielded cable which is not electrically connected to ground then what you have in an antenna.  Instead of reducing interference as intended, the ungrounded shielding in shielded cable actually increases interference.

Finally, the most common  thing to come up, Ethernet cable cannot be longer than 100 meters (about 328 feet).  Any longer than that and the signal starts to degrade.  If you need a longer cable then you need to add a switch to the middle of the run.  You can go up to 100 meters from one switch to the other, then another 100 meters to the next switch.