Telecom riser and voice cabling
Voice and low-speed backbone cabling still runs on multi-pair copper, and the pair count is decided by the building, not by the datasheet.
Choosing the pair count
The range covers 2, 8, 12, 25 and 50 pair constructions. In practice the pair count follows the riser schedule: a small building backbones on 25 pair, a campus riser on 50 pair, and 2 to 12 pair cables serve short backbone links, intercom and door-entry systems.
Conductors are solid annealed bare copper from 0.40 mm to 0.58 mm with HDPE insulation, laid up as twisted pairs and jacketed in PVC or HDPE. The electrical limits published here — DC resistance unbalance of 3 % or less, insulation resistance of at least 5000 Mohm.km, mutual capacitance of at most 6.6 nF per 100 m and pair-to-earth capacitance unbalance of at most 330 pF per 100 m — are what keep crosstalk between pairs under control as the pair count rises.
Indoor and outdoor jackets
Indoor risers use a PVC or HDPE jacket. Where the cable leaves the building or runs in a wet duct, the ODPE versions add a PE jacket and waterproof paper. Do not run an indoor jacket into weather and do not assume a PE jacket is fire rated for an internal riser.
Termination and documentation
Multi-pair cable is terminated on 110 or Krone blocks, and the pair sequence has to match the block labelling. Order the cable with the pair count marked on the reel and keep the reel labels with the as-built documentation — that label is what the installer returns to when a pair is suspected later.
What to send with an enquiry
Send the riser schedule (pair count per riser), the indoor or outdoor condition, and the total length. If the building is being handed over to a tenant, tell us the labelling convention so the reels and boxes can be marked to match.
