Eight wires and one order
Cut open a cable that joins computers. Inside are eight thin wires, in four twisted pairs. Each wire has a colour.
If you plug them into the connector in the wrong order, the cable looks fine and does not work.
There are two agreed orders. Learn them and you can read any cable.
Key words
| Word | What it means |
|---|---|
| Network | computers and devices joined together so they can share data |
| UTP | unshielded twisted pair: a copper cable of twisted wire pairs with no metal screen |
| Twisted pair | two wires twisted together to cut down interference |
| Straight-through | a cable wired the same at both ends |
| Crossover | a cable wired differently at each end, so send and receive swap |
| EIA/TIA-568 | the standard that sets the order of the wires in the plug |
| 8P8C | the eight position, eight contact plug used on network cables, often called RJ45 |
| RJ11 | a smaller plug with six positions, used for telephone lines |
| Category | a grade of copper cable, such as Cat 5e or Cat 6, that sets its speed limit |
| Fibre-optic cable | a glass or plastic cable that carries data as pulses of light |
| Ethernet | the standard way of sending data over cables in a local network |
The cells students fill in are left blank in this preview.
By the end of this lesson
Note
I can name the two wiring layouts, say when to use a straight-through or a crossover cable, and compare copper and fibre cables.
Starter
Have a go
Starter
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
Straight-through and crossover
A straight-through cable has the same wire order at both ends. Use it to join unlike devices, such as a PC to a switch.
A crossover cable has a different order at each end, so one end sends where the other listens. Use it to join like devices, such as a PC to a PC or a switch to a switch.
Most new devices swap the pairs for themselves, so a crossover is rarely needed now. You still need to know it.
Quick check
Have a go
Quick check
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.