Shielded Cable Types — Every Designator Decoded
The ISO/IEC 11801 shielding designators, decoded once and for all: before the slash is the overall shield, after the slash is the per-pair treatment. Six constructions cover everything sold — and the ambiguous legacy 'STP' label maps onto at least three of them, which is why the designator belongs in the spec instead.
Shielding constructions
| Designator | Overall shield | Pair shield | Common name | Typical use | Common categories |
|---|---|---|---|---|---|
| U/UTP | none | none | UTP | Offices and routes clear of electrical noise — the most-installed cable worldwide | Cat3, Cat5e, Cat6, Cat6A |
| F/UTP | foil | none | FTP | Runs near power, lighting, or moderate EMI; the common shielded Cat6A construction | Cat5e, Cat6, Cat6A (very common) |
| U/FTP | none | foil per pair | pair-shielded | Alien-crosstalk suppression in dense 10G bundles; data-center patching | Cat6A, Cat7-style |
| F/FTP | foil | foil per pair | — | High EMI plus alien-crosstalk control | Cat6A, Cat7, Cat8 (common) |
| S/FTP | braid | foil per pair | fully shielded | Industrial floors, motors and VFDs, broadcast — the maximum-shielding construction | Cat7 / Cat7A (always), Cat8, premium Cat6A |
| SF/UTP | braid + foil | none | — | Heavy external EMI without pair-level screening; legacy European shielded installs | Cat5e, Cat6 (legacy) |
The bonding obligation
Choosing a shielded construction buys a grounding requirement along with the foil: the shield must be continuous through every jack and panel, and bonded to the telecommunications grounding busbar per ANSI/TIA-607. One floated segment — a cheap unshielded coupler in the middle of an S/FTP run — quietly breaks the whole design. Budget shielded jacks, shielded panels, and the bond conductor when estimating, not just the cable delta. For which categories require shielding in the first place, see the category comparison.
Common questions
What does F/UTP mean?
Overall foil, unshielded pairs. The letters before the slash describe the shield under the jacket (U = none, F = foil, S = braid, SF = braid plus foil); the letters after describe each pair (UTP = bare, FTP = foil around each pair). F/UTP — a foil wrap around four bare pairs — is what most "shielded Cat6A" actually is, and what older spec sheets loosely called FTP.
What is the difference between FTP and STP?
"STP" is the problem: it is a legacy shorthand that has been applied to almost any shielded construction, from a single foil to braid-plus-per-pair-foil, which is exactly why the ISO/IEC designators exist. "FTP" conventionally means F/UTP (overall foil only). When a spec says STP, ask which construction it means — or better, write the designator.
Do shielded cables need to be grounded?
Yes — an ungrounded shield is an antenna, and can perform worse than no shield. Bond the shield at the patch panel to the telecommunications grounding system per ANSI/TIA-607 (a minimum 12 AWG bond from the shielded panel to the rack busbar). The far end typically grounds through the connected equipment; do not deliberately float it or earth it to a separate ground.
When is shielded cable worth it?
Three honest cases: measurable EMI (motor rooms, VFDs, industrial floors, broadcast), alien-crosstalk control in dense 10GBASE-T bundles (where U/FTP earns its keep), and specs that simply require it (Cat7-class and Cat8 have no unshielded construction). For a normal office plant, well-installed U/UTP Cat6/6A certifies fine — shielding bought "just in case" mostly buys termination labor and a bonding obligation.
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