Telecom Equipment, Installation and Cabling Practice
This domain tests rack, cable and termination work to a professional standard: correct pinouts, cable support, earthing, labelling and separation from power circuits.
Core rules
- T568B order: 1 orange/white, 2 orange, 3 green/white, 4 blue, 5 blue/white, 6 green, 7 brown/white, 8 brown. T568A swaps the orange and green pairs.
- A straight-through cable uses the same scheme at both ends, as for PC-to-switch. A crossover swaps pairs at pins 1-3 and 2-6 for legacy switch-to-switch links.
- Keep twists to within about 13 mm of the termination; excess untwisting causes crosstalk.
- Support cable in trays; respect a bend radius of at least four times the cable diameter; do not over-tighten ties.
- Separate data cable from mains; cross at right angles where unavoidable; earth racks and shields.
- Label both ends, leave service loops and test every link.
Worked example
A 24-port patch panel needs 24 permanent links and 24 patch cords. For terminations, order 24 RJ45 plugs plus 10% spare = 26.4, rounded up to 27 per end. Because the panel and switch are different devices, use straight-through T568B at both ends; a crossover would be wrong here. Record each port label, for example PP-01 to SW-01 port 1, before testing.
Traps
Using a crossover where straight-through is required; splitting the green pair incorrectly across pins 3 and 6; untwisting 5 cm of pair; running data and mains in one conduit; using solid cable as a flexible patch cord; skipping labelling.