IEC TR 63079:2017

Code of practice for hearing-loop systems (HLS)

IEC TR 63079:2017(E) gives recommendations for and guidance on the design, planning, installation, testing, operation and maintenance of a hearing-loop system (HLS) intended for communicating speech, music and/or other signals. It is mainly concerned with HLS for hearing enhancement, in which the signals are communicated to users of hearing aids equipped with magnetic pick-up coils.
This document does not apply to induction-loop systems which use a carrier frequency, nor to other systems for hearing enhancement purposes which do not use magnetic induction.

General Information

• Status: Published
• Publication Date: 31-Mar-2020
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 17.140.50 - Electroacoustics
• Technical Committee: TC 29 - Electroacoustics
• Drafting Committee: WG 22 - TC 29/WG 22
• Current Stage: PPUB - Publication issued
• Start Date: 02-May-2017
• Completion Date: 10-Apr-2017

Relations

• Amended By: IEC TR 63079:2017/AMD1:2018 - Amendment 1 - Code of practice for hearing-loop systems (HLS)
• Effective Date: 05-Sep-2023
• Amended By: IEC TR 63079:2017/AMD2:2020 - Amendment 2 - Code of practice for hearing-loop systems (HLS)
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC TR 63079 ®
Edition 1.0 2017-04
TECHNICAL
REPORT
colour
inside
Code of practice for hearing-loop systems (HLS)
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

IEC Central Office Tel.: [phone]
3, rue de Varembé Fax: [phone]
CH-1211 Geneva 20 [e-mail]
Switzerland www.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.

IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
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bibliographical information on IEC International Standards, electrical terms containing 20 000 terms and definitions in
Technical Specifications, Technical Reports and other English and French, with equivalent terms in 16 additional
documents. Available for PC, Mac OS, Android Tablets and languages. Also known as the International Electrotechnical
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The advanced search enables to find IEC publications by a 65 000 electrotechnical terminology entries in English and
variety of criteria (reference number, text, technical French extracted from the Terms and Definitions clause of
committee,…). It also gives information on projects, replaced IEC publications issued since 2002. Some entries have been
and withdrawn publications. collected from earlier publications of IEC TC 37, 77, 86 and

CISPR.
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also once a month by email. need further assistance, please contact the Customer Service
Centre: [e-mail].
IEC TR 63079 ®
Edition 1.0 2017-04
TECHNICAL
REPORT
colour
inside
Code of practice for hearing-loop systems (HLS)

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.140.50 ISBN 978-2-8322-4154-7

– 2 – IEC TR 63079:2017  IEC 2017
CONTENTS
FOREWORD . 7
INTRODUCTION . 9
1 Scope . 10
2 Normative references . 10
3 Terms, definitions, signs and symbols . 10
3.1 Terms and definitions . 10
3.2 Signs and symbols . 12
3.2.1 Symbol for an induction-loop . 12
3.2.2 Symbol for multiple loops . 12
3.2.3 Sign for display in premises where an HLS is installed and for HLS
equipment identification . 13
3.2.4 Identification of areas where reception of the HLS is not satisfactory . 13
4 General . 14
4.1 How to use this document . 14
4.1.1 Persons addressed . 14
4.1.2 Objectives . 14
4.2 Specialist advice . 15
4.3 Safety aspects . 15
4.4 Conforming to existing performance documents . 15
5 Technical advice . 15
5.1 Complying with this document . 15
5.2 Seeking technical advice . 15
5.3 The nature of the advice . 16
5.4 Professional (consultancy) advice . 16
6 Purpose of the system . 16
7 Choosing the system supplier . 16
7.1 General . 16
7.2 Approaching a contractor . 17
7.3 Approaching a manufacturer of HLS equipment . 17
7.4 Approaching a specialist consultant . 17
8 Contractual provisions . 17
8.1 Performance specification . 17
8.2 Verifying that the completed system delivers its intended performance . 17
8.3 Arbitration . 18
9 Classification of systems . 18
10 Design . 20
10.1 General . 20
10.2 Symbols . 20
10.3 Basic theory . 21
10.3.1 Production of a magnetic field . 21
10.3.2 Directional pattern of the magnetic field . 22
10.3.3 Uniformity of the magnetic field strength . 26
10.3.4 Reference points for magnetic field strength . 26
10.3.5 Relationship between the requirements of IEC 60118-4 and the
characteristics of hearing aids and speech signals . 27
10.3.6 Impedance of the loop . 28

10.3.7 Selection of the method of driving the loop . 29
10.3.8 Current-driven loop . 29
10.3.9 Voltage-driven loop . 30
10.3.10 Voltage-driven loop with high-level equalization . 31
10.3.11 Voltage-driven loop with low-level equalization . 33
10.3.12 Use of transformers . 33
10.3.13 Effects of building construction . 34
10.3.14 Electromagnetic compatibility (EMC) . 35
10.3.15 Tone signals . 37
10.3.16 Equalization, other than for compensating loop impedance
characteristics . 37
10.3.17 Multiple loops . 37
10.3.18 Protection of loop conductors . 40
10.3.19 Automatic gain control (AGC), compression, limiting, noise gating and
voice control . 40
10.3.20 Signal-to-noise ratio . 41
10.3.21 HLS for purposes other than assisted hearing . 42
10.4 System components . 42
10.4.1 Final amplifiers . 42
10.4.2 Preamplifiers and mixers . 42
10.4.3 Signal sources . 43
10.5 Objective measurement of intelligibility . 50
10.6 Safety and reliability considerations . 51
10.7 Designing for monitoring and maintenance . 51
10.8 External factors . 51
10.8.1 Magnetic noise interference . 51
10.8.2 Effect of metal in the building . 52
10.9 Magnetic field overspill . 52
10.10 The role of the system designer in commissioning . 52
11 Responsibility of the installer . 52
12 Installation practices and workmanship . 54
13 Inspection and testing of wiring . 55
14 Commissioning . 56
15 Documentation . 57
16 Certification . 58
17 Acceptance. 59
18 Verification . 60
19 Owner responsibilities . 60
19.1 Signage . 60
19.2 User feedback . 61
19.3 Staff training . 61
20 Operation and maintenance . 61
20.1 General . 61
20.2 Routine testing . 61
20.3 Inspection and servicing . 62
20.4 Non-routine attention . 63
20.5 Special inspection on appointment of a new maintenance organization . 63
20.6 Arrangements for repair of faults or damage . 63

– 4 – IEC TR 63079:2017  IEC 2017
20.7 Modifications to the system .
...

IEC TR 63079 ®
Edition 1.1 2018-09
CONSOLIDATED VERSION
TECHNICAL
REPORT
colour
inside
Code of practice for hearing-loop systems (HLS)

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

IEC Central Office Tel.: [phone]
3, rue de Varembé [e-mail]
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.

IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
The stand-alone application for consulting the entire The world's leading online dictionary of electronic and
bibliographical information on IEC International Standards, electrical terms containing 21 000 terms and definitions in
Technical Specifications, Technical Reports and other English and French, with equivalent terms in 16 additional
documents. Available for PC, Mac OS, Android Tablets and languages. Also known as the International Electrotechnical
iPad. Vocabulary (IEV) online.

IEC publications search - webstore.iec.ch/advsearchform IEC Glossary - std.iec.ch/glossary
The advanced search enables to find IEC publications by a 67 000 electrotechnical terminology entries in English and
variety of criteria (reference number, text, technical French extracted from the Terms and Definitions clause of
committee,…). It also gives information on projects, replaced IEC publications issued since 2002. Some entries have been
and withdrawn publications. collected from earlier publications of IEC TC 37, 77, 86 and

CISPR.
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published IEC Customer Service Centre - webstore.iec.ch/csc
details all new publications released. Available online and If you wish to give us your feedback on this publication or
also once a month by email. need further assistance, please contact the Customer Service
Centre: [e-mail].
IEC TR 63079 ®
Edition 1.1 2018-09
CONSOLIDATED VERSION
TECHNICAL
REPORT
colour
inside
Code of practice for hearing-loop systems (HLS)

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.140.50 ISBN 978-2-8322-6041-8

IEC TR 63079 ®
Edition 1.1 2018-09
CONSOLIDATED VERSION
REDLINE VERSION
colour
inside
Code of practice for hearing-loop systems (HLS)

– 2 – IEC TR 63079:2017+AMD1:2018 CSV
 IEC 2018
CONTENTS
FOREWORD . 7
INTRODUCTION . 9
1 Scope . 10
2 Normative references. 10
3 Terms, definitions, signs and symbols . 10
3.1 Terms and definitions . 10
3.2 Signs and symbols . 12
3.2.1 Symbol for an induction-loop . 12
3.2.2 Symbol for multiple loops . 13
3.2.3 Sign for display in premises where an HLS is installed and for HLS
equipment identification . 13
3.2.4 Identification of areas where reception of the HLS is not satisfactory . 14
4 General . 14
4.1 How to use this document . 14
4.1.1 Persons addressed . 14
4.1.2 Objectives . 14
4.2 Specialist advice . 15
4.3 Safety aspects . 15
4.4 Conforming to existing performance documents . 15
5 Technical advice . 15
5.1 Complying with this document . 15
5.2 Seeking technical advice . 16
5.3 The nature of the advice . 16
5.4 Professional (consultancy) advice . 16
6 Purpose of the system . 16
7 Choosing the system supplier . 17
7.1 General . 17
7.2 Approaching a contractor . 17
7.3 Approaching a manufacturer of HLS equipment. 17
7.4 Approaching a specialist consultant . 17
8 Contractual provisions . 18
8.1 Performance specification . 18
8.2 Verifying that the completed system delivers its intended performance . 18
8.3 Arbitration . 18
9 Classification of systems . 19
10 Design . 20
10.1 General . 20
10.2 Symbols . 21
10.3 Basic theory . 21
10.3.1 Production of a magnetic field . 21
10.3.2 Directional pattern of the magnetic field . 23
10.3.3 Uniformity of the magnetic field strength . 27
10.3.4 Reference points for magnetic field strength . 27
10.3.5 Relationship between the requirements of IEC 60118-4 and the
characteristics of hearing aids and speech signals . 28

 IEC 2018
10.3.6 Impedance of the loop . 29
10.3.7 Selection of the method of driving the loop . 30
10.3.8 Current-driven loop . 30
10.3.9 Voltage-driven loop . 31
10.3.10 Voltage-driven loop with high-level equalization . 32
10.3.11 Voltage-driven loop with low-level equalization . 34
10.3.12 Use of transformers. 34
10.3.13 Effects of building construction . 35
10.3.14 Electromagnetic compatibility (EMC) . 36
10.3.15 Tone signals . 38
10.3.16 Equalization, other than for compensating loop impedance
characteristics. 38
10.3.17 Multiple loops. 38
10.3.18 Protection of loop conductors . 41
10.3.19 Automatic gain control (AGC), compression, limiting, noise gating and
voice control . 42
10.3.20 Signal-to-noise ratio . 42
10.3.21 HLS for purposes other than assisted hearing . 43
10.4 System components . 44
10.4.1 Final amplifiers . 44
10.4.2 Preamplifiers and mixers . 44
10.4.3 Signal sources . 45
10.5 Objective measurement of intelligibility . 52
10.6 Safety and reliability considerations . 53
10.7 Designing for monitoring and maintenance. 53
10.8 External factors . 53
10.8.1 Magnetic noise interference . 53
10.8.2 Effect of metal in the building . 54
10.9 Magnetic field overspill . 54
10.10 The role of the system designer in commissioning . 54
11 Responsibility of the installer . 54
12 Installation practices and workmanship . 56
13 Inspection and testing of wiring . 57
14 Commissioning . 58
15 Documentation . 60
16 Certification . 60
17 Acceptance . 61
18 Verification . 62
19 Owner responsibilities . 63
19.1 Signage . 63
19.2 User feedback . 63
19.3 Staff training . 63
20 Operation and maintenance . 63
20.1 General . 63
20.2 Routine testing . 63
20.3 Inspection and servicing . 64
20.4 Non-routine attention . 65
20.5 Special inspection on appointment of a new maintenance organization . 65

– 4
...

IEC TR 63079 ®
Edition 1.2 2020-04
CONSOLIDATED VERSION
TECHNICAL
REPORT
colour
inside
Code of practice for hearing-loop systems (HLS)

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

IEC Central Office Tel.: [phone]
3, rue de Varembé [e-mail]
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform Electropedia - www.electropedia.org
The advanced search enables to find IEC publications by a The world's leading online dictionary on electrotechnology,
variety of criteria (reference number, text, technical containing more than 22 000 terminological entries in English
committee,…). It also gives information on projects, replaced and French, with equivalent terms in 16 additional languages.
and withdrawn publications. Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published IEC Glossary - std.iec.ch/glossary
details all new publications released. Available online and 67 000 electrotechnical terminology entries in English and
once a month by email. French extracted from the Terms and definitions clause of
IEC publications issued between 2002 and 2015. Some
IEC Customer Service Centre - webstore.iec.ch/csc entries have been collected from earlier publications of IEC
If you wish to give us your feedback on this publication or TC 37, 77, 86 and CISPR.

need further assistance, please contact the Customer Service

Centre: [e-mail].
IEC TR 63079 ®
Edition 1.2 2020-04
CONSOLIDATED VERSION
TECHNICAL
REPORT
colour
inside
Code of practice for hearing-loop systems (HLS)

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.140.50 ISBN 978-2-8322-8141-3

IEC TR 63079 ®
Edition 1.2 2020-04
CONSOLIDATED VERSION
REDLINE VERSION
colour
inside
Code of practice for hearing-loop systems (HLS)

– 2 – IEC TR 63079:2017+AMD1:2018
+AMD2:2020 CSV  IEC 2020
CONTENTS
FOREWORD . 7
INTRODUCTION . 9
1 Scope . 10
2 Normative references . 10
3 Terms, definitions, signs and symbols . 10
3.1 Terms and definitions . 10
3.2 Signs and symbols . 12
3.2.1 Symbol for an induction-loop . 12
3.2.2 Symbol for multiple loops . 13
3.2.3 Sign for display in premises where an HLS is installed and for HLS
equipment identification . 13
3.2.4 Identification of areas where reception of the HLS is not satisfactory . 14
4 General . 14
4.1 How to use this document . 14
4.1.1 Persons addressed . 14
4.1.2 Objectives . 14
4.2 Specialist advice . 15
4.3 Safety aspects . 15
4.4 Conforming to existing performance documents . 15
5 Technical advice . 15
5.1 Complying with this document . 15
5.2 Seeking technical advice . 16
5.3 The nature of the advice . 16
5.4 Professional (consultancy) advice . 16
6 Purpose of the system . 16
7 Choosing the system supplier . 17
7.1 General . 17
7.2 Approaching a contractor . 17
7.3 Approaching a manufacturer of HLS equipment . 17
7.4 Approaching a specialist consultant . 17
8 Contractual provisions . 18
8.1 Performance specification . 18
8.2 Verifying that the completed system delivers its intended performance . 18
8.3 Arbitration . 18
9 Classification of systems . 19
10 Design . 20
10.1 General . 20
10.2 Symbols . 21
10.3 Basic theory . 21
10.3.1 Production of a magnetic field . 21
10.3.2 Directional pattern of the magnetic field . 23
10.3.3 Uniformity of the magnetic field strength . 27
10.3.4 Reference points for magnetic field strength . 27
10.3.5 Relationship between the requirements of IEC 60118-4 and the
characteristics of hearing aids and speech signals . 28

+AMD2:2020 CSV  IEC 2020
10.3.6 Impedance of the loop . 29
10.3.7 Selection of the method of driving the loop . 30
10.3.8 Current-driven loop . 30
10.3.9 Voltage-driven loop . 31
10.3.10 Voltage-driven loop with high-level equalization . 32
10.3.11 Voltage-driven loop with low-level equalization . 34
10.3.12 Use of transformers . 34
10.3.13 Effects of building construction . 35
10.3.14 Electromagnetic compatibility (EMC) . 36
10.3.15 Tone signals . 38
10.3.16 Equalization, other than for compensating loop impedance

characteristics . 38
10.3.17 Multiple loops . 38
10.3.18 Protection of loop conductors . 41
10.3.19 Automatic gain control (AGC), compression, limiting, noise gating and
voice control . 42
10.3.20 Signal-to-noise ratio . 42
10.3.21 HLS for purposes other than assisted hearing . 43
10.3.22 Time-differences between related information streams . 44
10.4 System components . 44
10.4.1 Final amplifiers . 44
10.4.2 Preamplifiers and mixers . 44
10.4.3 Signal sources . 45
10.5 Objective measurement of intelligibility . 52
10.6 Safety and reliability considerations . 53
10.7 Designing for monitoring and maintenance . 53
10.8 External factors . 53
10.8.1 Magnetic noise interference . 53
10.8.2 Effect of metal in the building . 54
10.9 Magnetic field overspill . 54
10.10 The role of the system designer in commissioning . 54
11 Responsibility of the installer . 54
12 Installation practices and workmanship . 56
13 Inspection and testing of wiring . 57
14 Commissioning . 58
15 Documentation . 60
16 Certification . 60
17 Acceptance. 61
18 Verification . 62
19 Owner responsibilities . 63
19.1 Signage . 63
19.2 User feedback . 63
19.3 Staff training . 63
20 Operation and maintenance . 63
20.1 General . 63
20.2 Routine testing . 63
20.3 Inspection and servicing . 64
20.4 Non-routine attention . 65

– 4 – IEC TR 63079:2017+AMD1:2018
+AMD2:2020 CSV  IEC 2020
20.5 Special ins
...