The overall shield is mainly used for twisted pair cables. The overall shield design provides the best possible protection against electromagnetic interference for all cables featuring twisted pairs technology. This cable architecture is mainly used in data cables, thus ensuring the safest possible transmission of digital signals. In some cases, Ethernet cables (featuring twisted pair technology) up to category Cat 6 are also unshielded (UTP = Unshielded Twisted Pair). Although these UTP cables are generally less expensive and often more flexible to install, they are, nonetheless, often more susceptible to interference. For this reason, manufacturers of high-quality data cables often rely on twisted pair cables featuring overall shields (STP = Shielded Twisted Pair) whenever higher transmission frequencies are involved.
Overall cable shielding is available in different variants. Depending on which parts of the cable interior are shielded in which way and what the respective material properties are, there are various types with corresponding designations, which were uniformly specified in 2002 (international standard ISO/IEC 11801).
The most common variants are as follows:
- U/UTP denotes a completely unshielded cable.
- S/UTP: the wire pairs themselves are unshielded, but they are surrounded by an overall shield of braided wire strands.
- F/UTP cables also feature unshielded wire pairs, but the cable interior is encased in an overall foil shield.
- SF/UTP cables also feature "Unshielded Twisted Pairs" - but are additionally equipped with an overall shield consisting of a combination of braided wire and foil
- U/STP means that there is no overall shield, but the individual twisted wire pairs are encased in a wire braid shield instead
- S/STP means that the overall shield consists of braided wires and the wire pairs are also encased in a metal braided shield.
- Twisted pair cables with the designation F/STP feature an overall foil shielding and wire pairs with and additional braided shielding
- the designation SF/STP denotes an overall foil shielding plus wire braiding. The twisted pair cables are encased in a braided shielding
- U/FTP cables have no overall shielding and the wire pairs are encased in a foil shielding
- The combination "foil shielded wire pairs and an overall wire braid shield" is referred to as S/FTP
- F/FTP stands for foil in the overall shielding as well as foil wrapped around the wire pairs
- Last but not least, there are the SF/FTP cables featuring an overall foil shielding plus wire braiding and foil shielding wrapped around the twisted pairs.
So, in simplified terms, we can say that the "F" always stands for "foil", the "S" for the metal mesh/screening braid (usually consisting of copper) and the "SF" for the combination of the two.
So, to determine how the wire pairs should finally be enclosed and what type of overall shielding should be used depends on a large number of individual factors, thus representing the highest level, the "fine art" of cable development technology. The respective end product then again and again reveals that developing cables is a highly complex and diverse process. “No cable is alike!”
If you look ahead a little, you will definitely find that, to be on the safe side of a future with constantly increasing data rates and network requirements, you will always need the optimal, best-shielded cables you can possibly get your hands on.
