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Mitigation measures for







This handbook describes general principles and case studies of mitigation measures for telecom installations against electromagnetic disturbances. Mitigation of EMC problems related to emission and immunity, overvoltage and overcurrent are explained by actual examples that have occurred at telecom installations.

To solve the EMC problem, it is useful to examine when, where, and how the telecom installation, including equipment, is malfunctioning or damaged, and what noise sources are identified. It is also important to check immunity levels or resistibility levels of telecom installations before mitigation is carried out.

If a telecom installation satisfies the EMC recommendations as specified in ITU-T K-series Recommendations, then few EMC problems should occur. However, if several noise sources are superimposed, telecom equipment may malfunction or become damaged because there are many noise sources in the environment. Therefore, it is useful to remove major noise sources when solving EMC problems.

This handbook describes several methodologies to solve EMC problems, how to locate major noise sources, and mitigation tools/devices.
This handbook does not cover measurement methods or how to measure emissions, overvoltage or overcurrent; for those purposes, the relevant Recommendations and texts should be referred to. This handbook should be read in conjunction with the relevant Recommendations detailed below.

This handbook is composed of two parts. Part 1 describes the general principles of mitigation measures. Part 2, which groups the different case studies, is published as a hypertext and is freely available on ITU website. The different case studies may be downloaded and printed individually for convenience of use.

Part 1 is available from ITU publication website at

1 Scope

2 References

2.1 Basic guidelines

2.2 EMI

2.3 Overvoltage and overcurrent

3 Abbreviations

4 EM environment around/in a telecom installation

5 Noise sources and typical malfunction phenomena

5.1 Noise sources

5.2 Typical malfunction phenomena

6 Identification of noise sources

6.1 Environmental conditions

6.2 Malfunction patterns and related issues

6.3 Visual inspection

6.4 Functional tests and electrical characterization

6.5 Decapsulation and internal visual inspection

6.6 Fault site location techniques

7 Mitigation measures

8 Remarks on mitigation measures

8.1 Emission and immunity improvement

8.2 Overvoltage and overcurrent

9 Methodology for measuring and evaluating EM-environment

9.1 Measuring tools

9.2 Measuring EMI noise

9.3 Finding EMI sources

10 Procedures for solving EMC problems in the field

10.1 Items to be checked before considering EMI

10.2 Checking compliance with the requirements

10.3 Measuring the EM environment

10.4 Evaluating the EM environment and clarifying EMI sources

10.5 Procedure

Annex A Examples of mitigation measures

A.1 Applying mitigation measures to telephone

A.2 Applying mitigation measures to FAX

A.3 Applying mitigation measures to switching equipment

A.4 Applying mitigation measures to ADSL modem

Annex B Ancillary telecom equipment and installation of additional telephones

Annex C Basic protection configuration


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Updated : 2010-09-15