Shielded twisted-pair (STP) provides better noise protection than UTP cabling. However, compared to UTP cable, STP cable is significantly more expensive and difficult to install. Like UTP cable, STP uses an RJ-45 connector.
STP cable combines the techniques of shielding to counter EMI and RFI and wire twisting to counter crosstalk. To gain the full benefit of the shielding, STP cables are terminated with special shielded STP data connectors. If the cable is improperly grounded, the shield may act like an antenna and pick up unwanted signals.
Different types of STP cables with different characteristics are available. However, there are two common variations of STP:
- STP cable shields the entire bundle of wires with foil eliminating virtually all interference (more common).
- STP cable shields the entire bundle of wires as well as the individual wire pairs with foil eliminating all interference.
The STP cable shown uses four pairs of wires, each wrapped in a foil shield, which are then wrapped in an overall metallic braid or foil.
For many years, STP was the cabling structure specified for use in Token Ring network installations. With the decline of Token Ring the demand for shielded twisted-pair cabling also waned. However, the new 10 GB standard for Ethernet has a provision for the use of STP cabling which is providing a renewed interest in shielded twisted-pair cabling.