1、DRAFT FOR DEVELOPMENTDD CLC/TS 62367:2005Safety aspects for xDSL signals on circuits connected to telecommunication networks (DSL: Digital Subscriber Line)ICS 35.020g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g
2、48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58DD CLC/TS 62367:2005This Draft for Development was published under the authority of the Standards Policy and Strategy Committee on 23 December 2005 BSI 23 December 2005ISBN 0 580 47112 8National forewordThis Draft for Development is th
3、e English language version of CLC/TS 62367:2005. It is identical with IEC/TS 62367:2004.This publication is not to be regarded as a British Standard. It is being issued in the Draft for Development series of publications and is of a provisional nature because, although an international standard has
4、not been agreed, the content is important since it gives rules for dealing with the equipment mentioned in this specification in relation to the BS EN 60950 series of standards. It should be applied on this provisional basis, so that information and experience of its practical application may be obt
5、ained. Comments arising from the use of this Draft for Development are requested so that UK experience can be reported to the European organization responsible for its conversion to a European standard. A review of this publication will be initiated 2 years after its publication by the European orga
6、nization so that a decision can be taken on its status at the end of its 3-year life. Notification of the start of the review period will be made in an announcement in the appropriate issue of Update Standards.According to the replies received by the end of the review period, the responsible BSI Com
7、mittee will decide whether to support the conversion into a European Standard, to extend the life of the Technical Specification or to withdraw it. Comments should be sent in writing to the Secretary of BSI Technical Committee EPL/108, Safety of electronic equipment, at British Standards House, 389
8、Chiswick High Road, London W4 4AL, giving the document reference and clause number and proposing, where possible, an appropriate revision of the text.A list of organizations represented on this committee can be obtained on request to its secretary. Cross-referencesThe British Standards which impleme
9、nt international or European publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online.This publiction does no
10、t purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance with a Draft for Development does not of itself confer immunity from legal obligationsSummary of pagesThis document comprises a front cover, an inside front cover, the CLC/TS
11、 title page, pages 2 to 13 and a back cover.The BSI copyright date displayed in this document indicates when the document was last issued.Amendments issued since publicationAmd. No. Date CommentsTECHNICAL SPECIFICATION CLC/TS 62367 SPECIFICATION TECHNIQUE TECHNISCHE SPEZIFIKATION April 2005 CENELEC
12、European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B - 1050 Brussels 2005 CENELEC - All rights of exploitation in any form and by any means reserved worldwid
13、e for CENELEC members. Ref. No. CLC/TS 62367:2005 E ICS 35.020 English version Safety aspects for xDSL signals on circuits connected to telecommunication networks (DSL: Digital Subscriber Line) (IEC 62367:2004) Aspects de scurit pour signaux xDSL sur circuits connects aux rseaux de tlcommunication (
14、DSL: ligne dabonn numrique) (CEI 62367:2004) Sicherheitsaspekte fr xDSL-Signale in Stromkreisen fr den Anschluss an Telekommunikationsnetze (DSL: digitale Teilnehmerleitung) (IEC 62367:2004) This Technical Specification was approved by CENELEC on 2004-12-07. CENELEC members are required to announce
15、the existence of this TS in the same way as for an EN and to make the TS available promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force. CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech Rep
16、ublic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. Foreword The text of the Technical Specification IEC/TS 62367:2
17、004, prepared by IEC TC 108, Safety of electronic equipment within the field of audio/video, information technology and communication technology, was submitted to the formal vote and was approved by CENELEC as CLC/TS 62367 on 2004-12-07. The following date was fixed: latest date by which the existen
18、ce of the CLC/TS has to be announced at national level (doa) 2005-06-01 Annex ZA has been added by CENELEC. _ Endorsement notice The text of the Technical Specification IEC/TS 62367:2004 was approved by CENELEC as a Technical Specification without any modification. _ 1)Undated reference. 2)Valid edi
19、tion at date of issue. CLC/TS 62367:2005 2 3 CLC/TS 62367:2005 CONTENTS INTRODUCTION.4 1 Scope 5 2 Normative references .5 3 Terms, definitions and abbreviations.5 4 xDSL signals on circuits connected to telecommunication networks .6 Annex A (informative) xDSL telecommunication systems 7 A.1 Introdu
20、ction 7 A.2 General description 7 A.3 Peak-to average ratio and CF .8 A.4 CF distribution9 A.5 Line termination impedance 11 A.6 Measurement of xDSL parameters 11 Annex ZA (normative) Normative references to international publications with their corresponding European publications13 Bibliography .12
21、 Figure A.1 Typical configuration of an xDSL system7 Figure A.2 Typical xDSL (VDSL) signal in the time-domain .8 Figure A.3 Probability of symbol with CF x10 Figure A.4 Inter-arrival time of symbol with CF x (DMT-symbol rate = 4 kHz)10 CLC/TS 62367:2005 4 INTRODUCTION xDSL signals are high-speed tel
22、ecommunication signals that may be present on a telecommunication line, together with: analogue PSTN (Public Switched Telephone Network); ISDN (Integrated Services Digital Network) signals; or a d.c. power-feeding component. An xDSL signal is characterised by an amplitude of the order of 3 V r.m.s.
23、with superimposed spikes having very short duration (about 1 s) and peak values not exceeding 30 V. When combined with other services as above, the peak voltage can very occasionally exceed the limits for a TNV-3 CIRCUIT. However the excursions above these limits consist of these very short duration
24、 spikes. There are no published documents from IEC on the effect of such spikes on the human body, but experience with xDSL is that the safety risk, if any, is very small because of: the low power of the spikes; and the limited accessibility of TNV circuits. The amplitude and probability of the spik
25、es have been calculated as follows: amplitude up to 15V/1s with a probability of occurrence of one every few seconds to every few minutes; amplitude up to 20V/1s with a probability of occurrence of one every few hours; amplitude up to 27V/1s with a probability of occurrence of one every few years. A
26、nnex A gives more detail on the operation of xDSL telecommunication systems. 5 CLC/TS 62367:2005 SAFETY ASPECTS FOR XDSL SIGNALS ON CIRCUITS CONNECTED TO TELECOMMUNICATION NETWORKS (DSL: DIGITAL SUBSCRIBER LINE) 1 Scope This technical specification addresses the safety implications of having xDSL si
27、gnals on circuits in equipment connected to a TELECOMMUNICATION NETWORK, and gives rules for dealing with such equipment in the context of the IEC 60950 series. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, onl
28、y the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60950 (all parts), Information technology equipment Safety IEC 60950-1 (all parts), Information technology equipment Safety Part 1: General requirements 3 Terms
29、and definitions, and abbreviations For the purposes of this document, the terms and definitions in the IEC 60950 series and the following abbreviations apply. ADSL Asymmetric Digital Subscriber Line CF Crest Factor CO Central Office CPE Customer Premises Equipment DMT Discrete Multi Tone DSL Digital
30、 Subscriber Line HDSL High Speed Digital Subscriber Line IEC International Electrotechnical Commission ISDN Integrated Services Digital Network ITU International Telecommunication Union ITU-T Telecommunication Standardization Sector of ITU NT Network Termination PAR Peak to Average Ratio PSTN Public
31、 Switched Telephone Network QAM Quadrature Amplitude Modulation RSS Remote Signal Source SDSL Symmetric Digital Subscriber Line TNV Telecommunication Network Voltage VDSL Very-high-bit-rate Digital Subscriber Line CLC/TS 62367:2005 6 4 xDSL signals on circuits connected to telecommunication networks
32、 Based on the information presented in Annex A, it is recommended that for equipment within the scope of the IEC 60950 series of standards, the following rules be applied for xDSL signals on circuits connected to telecommunication networks. Rule 1: Circuits carrying xDSL signals are classified as ei
33、ther TNV-1 CIRCUITS or TNV-3 CIRCUITS, depending on the normal operating voltage of the circuit. Rule 2: When a) assessing the voltages in circuits carrying xDSL signals with respect to the limits in 2.3.1 of IEC 60950-1, and when b) determining the WORKING VOLTAGE of insulation in accordance with t
34、he IEC 60950 series, the voltage of xDSL signals is regarded as zero and has no impact on the classification of the circuits. 7 CLC/TS 62367:2005 Annex A (informative) xDSL telecommunication systems A.1 Introduction This annex describes the structure of xDSL signals, and explains why it is considere
35、d that there is no shock hazard associated with xDSL signals. xDSL is a general expression for high-speed telecommunication signals such as ADSL (Asymmetric Digital Subscriber Line), VDSL (Very-high-bit-rate DSL), HDSL (High-Speed- DSL), SDSL (Symmetric DSL), etc. (see Figure A.1). xDSL signals are
36、generally transmitted between the CO (Central Office) or RSS (Remote Signal Sources, such as repeaters and optical network units in street cabinets) and the CPE (customer premises equipment). These signals are transmitted over existing wires and cables. ADSL and VDSL signals may be transmitted in co
37、mbination with existing telephone services such as PSTN and ISDN. In other cases the telecommunication line only carries the xDSL signal together with d.c. to power the CPE from the CO. CO or RSS Equipment CO or RSSEnd modemCPE Access network Splitter DSLportSplitter CPE End modem PSTN-/ISDN- line I
38、SDN-NT or telephone Digital port PSTN-/ISDN portPSTN-/ISDN portDigitalport DSLportLine loop IEC 029/04 Figure A.1 Typical configuration of an xDSL system A.2 General description An xDSL signal consists of an a.c. waveform with complex amplitude and frequency behaviour due to the use of special modul
39、ation techniques. Although xDSL signals are functional communication signals within a broadband frequency spectrum, their appearance on an oscilloscope is like “white-noise”, for example, a small average or r.m.s. value with occasional spikes (see Figure A.2). CLC/TS 62367:2005 8 r.m.s.valueequals1V
40、DSL transmission6 400 6 600 6 800 7 000 7 200 7 400 7 600Time s432101234IEC 030/04Figure A.2 Typical xDSL (VDSL) signal in the time-domain The magnitude of an xDSL signal is defined in the relevant functional standard by its mean power into a resistive load, within a specified frequency band. This m
41、ean power, in dBm, can be expressed as a well defined r.m.s. voltage value, in general in the order of a few volts. Of all xDSL signals, the worst case value, for ADSL combined with PSTN (ITU-T Recommendation G.992.1- Annex A), is 20,4 dBm into 100 or 3,31 V r.m.s. in the downstream direction (from
42、CO to CPE), and 12,5 dBm into 100 or 1,33 V r.m.s. in the upstream direction (from CPE to CO). The peak voltage however can be higher and depends on: peak-to average ratio (PAR) or crest factor (CF); CF distribution; real line-termination impedance, which is not purely resistive. In A.3 and A.4 belo
43、w, an explanation is given to show that: the value of the peak voltage is limited and the higher the value of the peak voltage, the lower probability of its occurrence. A.3 Peak-to average ratio and CF As the name indicates, the PAR of a symbol is the ratio of the maximum instantaneous power in the
44、symbol to the average power. Without giving detailed information about a symbol, it is an indication for the occurrence of peaks in that symbol. A large PAR value indicates that somewhere in the signal at least one sample takes on a (power) value that is large with respect to the average sample powe
45、r. A small PAR value on the other hand indicates that the symbol varies evenly around the average power, without making any large excursions. 9 CLC/TS 62367:2005 The CF is mostly used in standardization documents instead of the PAR. The CF is defined as the square root of the PAR (or half the PAR wh
46、en the value is expressed in dB). In practice, ADSL systems are designed to cope with a CF of about 5 to 6. The probability of peak voltages above a certain threshold can be estimated by using the CF distribution. The relation is given by: Vpeak= CF x V r.m.s.Since the CF is stochastic in the xDSL m
47、ulti-carrier modulation, the same will be true for the peak voltage of the signal (evaluated over a limited period of time). Given the worst case signal type, which is ADSL, and the assumption that upstream and downstream ADSL signals are cumulative on the telecommunication lines, the signal can the
48、oretically go up to 27,8 Vpeak, with a CF of 6. However, this peak voltage has only a very low probability of occurrence. A.4 CF distribution Figure A.3 shows the CF distribution of xDSL signals using two different modulation techniques, namely a Quadrature Amplitude Modulation (QAM) and a multi-car
49、rier Discrete MultiTone (DMT). The figure is based on a Gaussian distribution and shows the relation between the probability (value in y-axis) that an xDSL signal has a CF larger than x (value in x-axis). The simulation was done with a non-resistive line impedance termination and shows a simulation for 24, 256 and 4 096 carriers or tones. The figure shows that, if the number of carriers increases in a multi carrier DMT system, the probability that a signal with a
