【正文】 orated, it shall be in contact with the main screen element. The drain wire shall be either solid or stranded, made of plain or metalcoated copper. Care should be taken when placing dissimilar metals in contact with each other. Coatings or other methods of protection may be necessary to prevent galvanic interaction. A protective wrapping may be applied under and/or over the screen. Moisture barriers To minimise moisture permeation through the sheath, a longitudinal overlapped metallic foil may be used which is bonded to the inner surface of an extruded plastic sheath. Protective wrappings W hen required by the relevant sectional specification, a protective wrapping shall be provided. – 9 – EN 502881:2020 Sheath Sheath material(s) shall meet the requirements of the relevant part of EN 502902 or otherwise as detailed in the appropriate sectional specification. The sheath shall be continuous, having a thickness as uniform as possible. The thickness of the sheath shall be determined according to the method specified in of EN 6081111. Bedding layers for metallic protection W hen metallic protection is required, the relevant sectional specification shall give details of the bedding. Metallic protection W hen required by the relevant sectional specification, and according to of EN 5029021, the armouring shall consist of one or more of the following: a layer of round or flat galvanised steel wires (a counter helix of tape is permitted) a single or a double layer of steel or brass tapes a galvanised steel or tinned copper wire braid Integral suspension strand W hen required, the integral suspension strand shall be in accordance with of EN 5029021 and shall meet the requirements of the relevant sectional specification. Oversheath The choice of the sheath material shall take into account electrical and environmental requirements. Sheath material(s) shall meet the requirements of the relevant part of 502902 or otherwise as detailed in the appropriate sectional specification. The sheath shall be continuous, having a thickness as uniform as possible. The thickness of the sheath shall be determined according to the method specified in of EN 6081111. Fauna protection The relevant sectional specification shall indicate details of the protection required to protect the cable against attack by fauna (such as rodents or insects). The protection may be a choice of armouring (), special wrapping tape (), outer sheath material () or any bination of these. Chemical and /or environmental protection W hen required, a protection against chemical hazards and/or environmental effects shall be provided. EN 502881:2020 – 10 – It may consist of one or more of the following: a metallic sheath of lead or suitable lead alloy。 a plain or coated metal braid。r analoge und digitale 220。 233。BRITISH STANDARD BS EN 502881:2020 Multielement metallic cables used in analogue and digital munication and control — Part 1: Generic specification The Europe an Standard EN 502881:2020 has the status of a British Standard ICS Amd. No. Date Comments BS EN 502881:2020 National foreword This British Standard is the official English language version of EN 502881:2020. It supersed es BS EN 502881:2020 which is withdraw n. The UK particip ation in its preparation was entrusted by Technical Committee EPL/46, Cables, wires, waveguid es, . connectors, . and microwave passive ponents and accessories, to Submitt ee EPL/46 /1, Co mm unication cables, which has the responsibility to: — aid enquirers to understand the text。talliques 224。rique Mehradrige metallische Daten und Kontrollkabel f252。 a metal tape laminated to a plastic tape。 a multilayer sheath of an aluminium tape and polyolefin, . high density polyethelyne or polyamide. The sheath shall be continuous, having a thickness as uniform as possible. The thickness of the sheath shall be determined according to the method specified in of EN 6081111. 5 Test methods for pleted cables As required by the relevant sectional specification, test methods selected from those listed below shall be applied. Electrical test methods Lowfrequency and . electrical measurements Subclause no. Parameter Test method Standard Part no. Conductor resistance EN 502891 2 Conductor resistance unbalance EN 502891 2 Dielectric strength EN 502891 3 Insulation resistance EN 502891 4 Mutual capacitance EN 502891 5 Capacitance unbalance EN 502891 5 Inductance EN 502891 12 Inductance to resistance ratio EN 502891 12 – 11 – EN 502881:2020 Highfrequency electrical and transmission measurements Subclause no. Parameter Test method Standard Part no. Velocity of propagation EN 502891 7 or 11 Propagation delay difference (skew) EN 502891 7 or 11 1) Longitudinal attenuation EN 502891 8 Longitudinal conversion loss (LCL) EN 502891 9 Nearend crosstalk (NEXT) EN 502891 10 Farend crosstalk (FEXT) EN 502891 10 Power sum (PS) of crosstalk loss EN 502891 10