1 Introduction edit wire conductor wire wrapped externally have called shielded cable. Structure called the shield conductor wrapped, usually conductive fabric, woven copper mesh or copper (aluminum) platinum. Application shield earthed external interference signal may be the layer into the earth, to avoid interference with the interference signal into the inner conductor while reducing the loss of the transmission signal. 2 Note the use of shielded cable shield editor does not allow multi-point grounding, because different ground is not always the same, the potential difference between the points exist. The multi-point grounding, shielding layer current, induced to form the current on the wire, induction to interfere with the signal line, not only would not achieve the shielding effect, but the introduction of interference, especially in the use of multi-inverter occasions, contains interference a variety of high-order harmonic components, resulting in a greater impact, should pay special attention.