100 being adopted more in engine and battery compartments for their heat resistance properties. They also exhibit significant low-temperature toughness, abrasion resistance and radiation resistance, while also having lower hardness and rigidity than conventional polymers (enabling greater flexibility). The exact process of cross-linking refers to creating bonds between polymer chains within the material, and can take the form of different chemical reactions, including the use of electron beams, peroxide and silanes. More unusual options have included heat shrink tubing material with silver embedded in it. While the material remains non-conductive, it integrates a degree of EMI protection directly into the jacket material without necessarily using a conventional shielding component. Shielding Materials and components used for shielding in modern cable harnesses continue to consist largely of aluminium foils and braids. Modern approaches to shielding include a growing popularity of combining a braid and a foil across the length of a harness (the former providing 85% EMI protection, the latter 100%). The total quantity and hence cost of aluminium shielding can be minimised by using shielded twisted pairs (STPs), which are an increasingly popular harness design for dedicated high-speed comms or LAN connections. In these applications, power and low-speed comms are not combined within the harness, and can reduce the overall use of shielding by limiting the use of aluminium shields to those commsheavy cables that need them most to prevent signal interference. A typical STP cable harness contains multiple twisted pairs, each pair having its own individual shielding to minimise interference between them. The term has also however been used to describe cables with multiple twisted pairs, each individually unshielded but with a single foil or braid shielding encompassing all of them, concentrically and just inside the final protective outer jacket. Beyond this are many terms for the various combinations of shielding approaches to high-speed twisted pair cabling. S/UTP (shielded/unshielded twisted pair) for instance can be used to describe designs in which the twisted pairs are shielded collectively but not individually. When they are shielded individually with foil, they are often called foil twisted pairs (FTPs), although FTP foils are light and therefore prone to tearing during integration and routing if tugged or bent excessively. Conversely, S/FTPs (shielded/foil twisted pairs) specifically describe those instances where twisted pairs are shielded individually and collectively. Foil is applied at the individual level, and a thick braided shield around the outside makes the cable more resilient to bending or pulling damage during installation. There are many other permutations, such as F/UTP, when a foil is used collectively with no individual EM protection, or SF/UTP where both foil and braid are applied at the outer level about the individually unshielded twisted pairs. Cable management When routing cables throughout avionics bays or other vehicle sections, it is common to use a wide range of external components such as cable tie straps, slotted panels, P-clamps or T-clamps that can be fastened to walls, brackets or bulkheads. October/November 2023 | Uncrewed Systems Technology Shielding can now be weaved automatically, applied to individual twisted pairs or combined with foils depending on the exact EMI protection needed (Courtesy of Omnetics) Fibre optic cables are expected to grow in popularity for the very high speed, highly secure data comms they enable (Courtesy of LEMO)
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