What is the use of the double shielded patch cable?

Twisted pair can be divided into shielded twisted pair and unshielded twisted pair, unshielded twisted pair without shielding jacket, small diameter, save the space occupied; Light weight, easy to bend, easy to install, so most local area networks use unshielded twisted pair as the transmission medium for wiring to network, Network Cable by a certain distance long twisted pair and RJ45 head composition.

Shielded twisted pair bread with a layer of metal shielding film, its anti-interference performance is better. But the shielded twisted-pair requires that the whole system is all shielded devices, including cables, sockets, crystal heads and distribution frames, and the building needs to have a good grounding system. But in the actual construction, it is difficult to perfect grounding, so that the shielding layer itself becomes a great source of interference, resulting in performance far worse than the non-shielded twisted pair wire. Therefore, unless specifically required, only unshielded twisted pair wires are usually used in integrated cabling systems.

Twisted pair can be shielded in many ways:
1. The four pairs of wires are only wrapped in aluminum foil -- single shielded cable, only with a layer of insulation in the outer sheath, and a layer of shielding for each core wire and a layer of shielding for all the core wires (inside the sheath).
2. Each pair of wires is wrapped with aluminum foil, and there is no metal net outside the four pairs of wires;
These two types are commonly referred to as singly shielded twisted pair.
3. Use aluminum foil and metal mesh to wrap the four pairs of wires;
4, each pair of lines with aluminum foil wrapped, four pairs of lines plus metal mesh.
The latter two are generally known as double shielded twisted pair, aluminum foil is anti-high frequency interference, metal mesh is anti-low frequency interference.
That is, the dual shielded network cable is each core wire has a layer of shielding, and then in all the core wire outside (inside the sheath) and a layer of shielding layer.