Which cable is this?
A cupboard holds sixty blue cables, all tied in one bundle. Only one goes to the manager's desk. Pulling them one by one would take all day.
A cabling team uses a small tool that makes one cable "sing". Different questions need different tools.
Key words
| Word | What it means |
|---|---|
| Multimeter | a hand tool that reads voltage, resistance and continuity |
| Continuity | a clear path for current from one end of a wire to the other |
| Tone generator | a unit that puts a sound signal on a cable |
| Probe | a wand that picks up the tone to find the cable |
| OTDR | optical time domain reflectometer, which sends light pulses along fibre and reads what comes back |
| Light source | a unit that sends a steady light into a fibre |
| Power meter | a unit that reads how much light arrives |
| Spectrum analyser | a unit that shows signal strength at each frequency |
| Continuity tester | a simple unit that checks each wire joins end to end |
| Resistance | how much a wire holds back current, in ohms |
The cells students fill in are left blank in this preview.
By the end of this lesson
Note
I can say what each of six testing tools measures, and pick the right one for a cable question.
Starter: copper and fibre
Have a go
Starter: copper and fibre
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
Tools for copper cable
A multimeter has a dial for several jobs. On a cable it reads resistance and it beeps for continuity. It tells you a wire is whole. It does not tell you how fast the cable is.
A tone generator and probe work as a pair. The generator sends a tone down a cable. The probe, held near the far end, squeals when it is close to that cable.
Continuity tester and spectrum analyser
A continuity tester is a small unit with a lead at each end. It checks that each wire runs end to end, and many show which wire is which. It finds a break, but it cannot prove a cable is good for fast data.
A spectrum analyser shows how strong a signal is at each frequency. Installers use it to find a source of noise, such as a motor or a radio.
Check: copper tools
Have a go
Check: copper tools
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.