Ten metres short
An installer pulls the last cable of the day and finds the drum is empty. The wall socket is still ten metres away. A van trip, a lost afternoon and an angry customer follow.
A few sums at the start of the job stop this. Quantities are worked out before anything is bought.
Key words
| Word | What it means |
|---|---|
| Requirement | something the customer needs |
| Route length | the distance a cable travels from outlet to rack |
| Slack | extra cable left at each end for fitting and repair |
| Drum | a box or reel that holds a length of cable |
| Port | a socket on a patch panel or switch |
| Spare capacity | extra room kept for growth |
| Patch panel | a frame of ports where the fixed cables end |
| Resources | people, kit and materials a job needs |
| Percentage | a number out of every 100 |
The cells students fill in are left blank in this preview.
By the end of this lesson
Note
I can gather requirements, work out whole-number quantities of cable, ports and panels, and spot the issues a plan may hide.
Starter: the specification
Have a go
Starter: the specification
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
Gather the requirements first
Ask the customer short, clear questions before any sums.
How many users? How many outlets in each room? How fast must the links be? Are there phones, cameras or Wi-Fi points that need power over the cable? Where is the rack? How much will the site grow in five years?
Resources and place
Then list the resources: how many people, for how many days, with which tools and software. Check the location of each part: where the outlets and rack go, where the cable will run, and how far each run is.
Measure the real route, not a straight line. A cable goes up the wall, along the ceiling and down again.
Worked example: cable for three runs
| Run | Route length | Slack added | Cable needed |
|---|---|---|---|
| Outlet 1 | 30 m | 5 m | 35 m |
| Outlet 2 | 45 m | 5 m | 50 m |
| Outlet 3 | 60 m | 5 m | 65 m |
| Total | 135 m | 15 m | 150 m |
The cells students fill in are left blank in this preview.
Check: cable for the runs
Have a go
Check: cable for the runs
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.