What is the cable  Screening ?

ELECTRICAL INTERFERENCE IN CABLES.

All cables are subject to interference pickup as a result of electrostatic and electro-magnetic fields set up by nearby electrical wiring and equipment.

There are two basic types of external noise that affect cables:

1. Electrostatic, from external high voltages

2. Electromagnetic, from external high currents

Electrostatic noise

This type of interference is reduced by adding a total coverage screen: around the cable (core screen, CS), around each pair of wires (element screen, ES), or both (ESCS).

The two most important characteristics of this type of static screen are that it has total coverage and has a low resistance path to earth. The circumferential resistance around the screen may be quite high, as electrically induced voltages do not produce circumferential currents. This permits the use of laminate or conducting plastics of relatively high resistance in association with drainwires to reduce the longitudinal resistance.

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