IEC 62489-1:2010/AMD1:2014

IEC 62489-1 ®
Edition 1.0 2014-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
AM ENDMENT 1
AM ENDEMENT 1
Electroacoustics – Audio-frequency induction loop systems for assisted
hearing –
Part 1: Methods of measuring and specifying the performance of system
components
Électroacoustique – Systèmes de boucles d’induction audiofréquences pour
améliorer l'audition –
Partie 1: Méthodes de mesure et de spécification des performances des
composants de systèmes
IEC 62489-1:2010-01/AMD1:2014-12(en-fr)

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IEC 62489-1 ®
Edition 1.0 2014-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
AM ENDMENT 1
AM ENDEMENT 1
Electroacoustics – Audio-frequency induction loop systems for assisted

hearing –
Part 1: Methods of measuring and specifying the performance of system

components
Électroacoustique – Systèmes de boucles d’induction audiofréquences pour

améliorer l'audition –
Partie 1: Méthodes de mesure et de spécification des performances des

composants de systèmes
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
M
CODE PRIX
ICS 17.140.50 ISBN 978-2-8322-1957-7

– 2 – IEC 62489-1:2010/AMD1:2014
© IEC 2014
FOREWORD
This amendment has been prepared by IEC technical committee 29: Electroacoustics.
The text of this amendment is based on the following documents:
FDIS Report on voting
29/853/FDIS 29/860/RVD
Full information on the voting for the approval of this amendment can be found in the report
on voting indicated in the above table.
The committee has decided that the contents of this amendment and the base publication will
remain unchanged until the stability date indicated on the IEC web site under
"http://webstore.iec.ch" in the data related to the specific publication. At this date, the
publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
_____________
CONTENTS
Add the titles of the new Clauses 9 and 10 and their subclauses as follows:
9 Neck loops
9.1 Input voltage
9.1.1 Characteristic to be specified
9.1.2 Method of measurement
9.2 Input impedance
9.2.1 Characteristic to be specified
9.2.2 Method of measurement
9.2.3 Recommended values
9.3 Frequency response
9.3.1 Characteristic to be specified
9.3.2 Method of measurement
9.3.3 Presentation of results
9.3.4 Connector
10 Monitoring devices
10.1 General
10.2 Recommendations for fixed devices
10.3 Recommendations for portable devices
Add the titles of the new Annexes D, E and F as follows.

© IEC 2014
Annex D (informative) Neck loops
Annex E (normative) Test jig for measuring the performance of neck loops
Annex F(normative) Specifications for loop listeners and assistive listening devices (ALDs)
Add, in the list of figures, the titles of new Figures E.1, E.2, E.3, E.4 and F.1 as follows.
Figure E.1 – Side view
Figure E.2 – Front view
Figure E.3 – Back view
Figure E.4 – Arrangement of the neck loop on the jig
Figure F.1 – Target frequency response
Add, in the list of tables, the title of the new Table 1, as follows.
Table 1 – Types of fixed monitoring device
2 Normative references
Add the following new references:
IEC 60417, Graphical symbols for use on equipment (available at http://www.graphical-
symbols.info/equipment)
IEC 60603-11, Connectors for frequencies below 3 MHz for use with printed boards – Part 11:
Detail specification for concentric connectors (dimensions for free connectors and fixed
connectors)
Replace the reference to "IEC 60268-3:2000", with the following updated reference:
IEC 60268-3:2013, Sound system equipment – Part 3: Amplifiers
3 Terms and definitions
Add, after 3.1 the following new terms and definitions:
3.2
phased loop array
system of neighbouring loops in which the currents are not in phase with each other
3.3
neck loop
small induction loop intended to be worn around the neck
NOTE See Annex D.
3.4
telecoil
magnetic pickup coil intended to receive signals from an induction-loop system in accordance
with IEC 60118-4
NOTE A telecoil can be part of a hearing aid or of any other device for receiving signals for an induction-loop
system in accordance with IEC 60118-4.

– 4 – IEC 62489-1:2010/AMD1:2014
© IEC 2014
3.5
loop listener
system consisting of a portable amplifier incorporating a telecoil and headphones or
earphones, intended to receive signals from an induction-loop system in accordance with
IEC 60118-4
NOTE The functions of loop listener and assistive listening device (see 3.6) can be combined.
3.6
assistive listening device
ALD
system consisting of a microphone, a portable amplifier and headphones, earphone or a neck
loop
NOTE 1 This device is not the portable receiver described in Annex E of IEC 60118-4:2006, which includes
measurement of magnetic field strength but no compensation for frequency-dependent hearing loss and AGC.
NOTE 2 This note applies to the French language only.
5.1 General
Replace, in the Note, the reference to IEC 60268-3:2000 with the updated reference to
IEC 606268-3:2013 as follows:
NOTE For characteristics not mentioned in this standard, the provisions of IEC 60268-3 can be applied, with the
provisions of 5.2 of this standard replacing those of 3.1 of IEC 60268-3:2013.
Add, after 5.4.13.3, the following new subclause:
5.4.13.4 Recommendations
It is strongly recommended that the amplifier should include automatic gain control with an
input level range of at least 32 dB for a maximum output level change of 3 dB. The total
harmonic distortion plus noise of the output current over this range should not exceed 5 %.
5.4.14 Phase error of quadrature networks for phased loop arrays
Replace all the existing subclauses by the following new subclauses:
5.4.14.1 Explanation
The primary means of reducing the overspill of the magnetic field of an AFILS to places where
it is not wanted is to reduce loop dimensions. If two or more adjacent small loops are
operated simultaneously in order to increase the useful magnetic field volume, the magnetic
fields partially or completely cancel in some places, creating unacceptable 'nulls', unless the
identical currents in the loops are decorrelated (forced to be 'out of step'). This can be
achieved in two ways:
• by delaying the current in one loop with respect to the other;
• by shifting the phase of the current in one loop by approximately 90° with respect to the
other.
The latter method is more commonly used. The phase difference needs to be near (but not
very precisely) 90°. The two fields create a rotating field (direction) vector, whose tip
describes a circle if the two fields are equal and at 90°. If not, it describes an ellipse, so that
the combined field is more irregular in space. If the two fields are not at 90° phase, one can
be considered as having a reference phase angle of 0°, the other having a relative phase
angle X. This field can be resolved into an in-phase component cos X and a quadrature
component sin X. The interaction of the in-phase component and the reference field tends to
produce the nulls in the vertical component of the field that would happen with no phase
difference. However, for small deviations from 90°, the effect is minimal. For example,

© IEC 2014
cos 85° = 0,087, so the in-phase field is increased or decreased by 0,72 dB, depending on
where the measurement is taken; in some places the fields add; in others they subtract.
5.4.14.2 Characteristic to be specified
The maximum deviation from 90° of the phase angle between the loop currents over the
frequency range 100 Hz to 5 kHz.
5.4.14.3 Method of measurement
See 14.11.4 of IEC 60268-3:2013. The loop currents may be measured by including a very
low value resistor in series with each loop and measuring the voltage across it. A 2-channel
audio analyser with balanced inputs may be used, or an oscilloscope. Because neither end of
the resistor is likely to be at earth potential, a simple balanced follower may be included
between the resistor and the input of the oscilloscope.
5.4.14.4 Presentation of results
The maximum deviation in degrees and the associated frequency or frequencies shall be
stated.
Insert, after Clause 6, the following new Clauses 9 and 10:
9 Neck loops
NOTE See Annex D for explanation and information and Annex B of IEC 60118-4:2006 for details of measurement
procedures.
9.1 Input voltage
9.1.1 Characteristic to be specified
The input voltage required to produce a magnetic field strength of 400 mA/m at the telecoil
position of a BTE hearing aid.
9.1.2 Method of measurement
The neck loop shall be arranged on the test jig specified in Figures E.1 to E.4. The telecoil or
inductor shall be approximately 3 mm diameter by 10 mm long, approximating the size of a
real telecoil in a behind-the-ear hearing aid.
The input voltage required to produce a magnetic field strength of 400 mA/m at 1 kHz shall be
measured and stated as the result.
9.2 Input impedance
9.2.1 Characteristic to be specified
The smallest magnitude of the input impedance over the frequency range 100 Hz to 5 kHz,
rounded to the nearest 1 Ω.
9.2.2 Method of measurement
The smallest magnitude of the input impedance over the frequency range 100 Hz to 5 kHz
shall be determined by any convenient means of sufficient accuracy.

– 6 – IEC 62489-1:2010/AMD1:2014
© IEC 2014
9.2.3 Recommended values
Recommended values for the rated input impedance (i.e. the value stated by the
manufacturer) are 8 Ω, 16 Ω and 32 Ω. Intermediate values are also acceptable. Higher
impedances are likely to be compatible with a wider range of sources.
9.3 Frequency response
9.3.1 Characteristic to be specified
The frequency response of the magnetic field strength at the reference point of the test jig
described in Annex E. The magnetic field strength is measured with a field strength meter
having an external probe formed by a telecoil or small inductor. The probe output requires
equalization so as to give a constant output voltage, independent of frequency (within 0,2 dB),
at least from 100 Hz to 5 kHz.
9.3.2 Method of measurement
The rated input voltage shall be applied from a low-impedance (less than 0,4 Ω) source.
Measurements of the magnetic field strength may be made by a continuous (or quasi-
continuous, e.g. 100 steps) swept frequency or at one-third-octave intervals.
9.3.3 Presentation of results
Results should preferably be presented as a graph. For presentation as text, the frequencies
at which the response differs from that at 1 kHz by 3 dB shall be stated.
9.3.4 Connector
9.3.4.1 Type of connector
It is recommended to fit a 3,5 mm 3-contact concentric connector in accordance with
IEC 60603-11, as this is compatible with the majority of types of signal source.
9.3.4.2 Connection
It is inadvisable to connect the tip and ring contacts directly, or via a 1:1 transformer. While
some sources tolerate this type of connection, not all do. It is therefore recommended to
include some resistance between the tip and ring connections.
10 Monitoring devices
10.1 General
A fixed monitoring device should be sited so that non-technical staff and/or members of the
public can easily verify whether the AFILS is working. In auditoria, care should be taken such
that the audible and/or visible output is not distracting and the monitor output may also be
relayed to the sound system control point.
Portable monitor devices should be used for checking the performance of the system in all
parts of the coverage area, on a routine basis and after any changes have been made to the
system or the building, or potential sources of interference have been introduced.
10.2 Recommendations for fixed devices
10.2.1 Fixed devices should conform to one of the recommendations in Table 1.

© IEC 2014
Table 1 – Types of fixed monitoring device
System active
Monitor type Meter Receiver Remote monitor
indicator
Purpose Promote user and Regular system Regular system Continuous system
staff awareness maintenance maintenance monitoring
Detection method Amplifier power
(see 10.2.2) supply, amplifier Loop current or Loop current or Loop current or
status, loop current magnetic field magnetic field magnetic field
or magnetic field signals signals signals
signals
Indication
System status Field strength Field strength Field strength
(see 10.2.3)
Auditory X X Loudspeaker (if non-
(see 10.2.4) technical staff
Loudspeaker, or
and/or the public
headphones
have access) or
headphones
Remote X X X Dry contact, audio,
(see 10.2.5) or data signal
10.2.2 The device may sense the magnetic field of the loop, the loop current, or have a
direct connection to the amplifier – depending on the intended purpose of the system. The
manufacturer's specification should state the method of sensing. The direction of maximum
response of any magnetic pick-up device should be marked on the equipment enclosure.
NOTE A magnetic-field sensing device can be more easily added to an existing installation, where the loop
conductor is not easily accessible, but it can only be sited where the magnetic field strength and direction are
suitable. A current-sensing device can be sited anywhere, and not require an external power source, but it is not
impossible for the loop current to be present while the magnetic field strength is not satisfactory due to a short-
circuit fault in the loop wiring.
For a magnetic-field sensing device, the manufacturer is free to choose any direction; the horizontal component of
the magnetic field can be sensed instead of the vertical, or an option provided. However, the variation of vertical
field at the edges of rooms can mean that a horizontal coil (pointing to the centre of the loop) is the most
appropriate.
In order to provide a suitable signal for use, it might also be necessary to filter out background noise due to AC
power systems.
10.2.3 The device should provide an illuminated signal to show that it is in operation and
another to show that it is receiving an adequate magnetic field strength.
NOTE As fixed monitor devices can be situated outside the useful volume of a loop installation, the input
sensitivity might need to be adjustable to accommodate a wide range of magnetic field strengths. A lockable preset
gain control could be provided for setting the sensitivity after the system itself has been commissioned.
10.2.4 If an audible output is provided, a lockable preset gain control, which cannot reduce
the audio output to zero, should be provided. This should be adjusted during the
commissioning of the device so that a clearly audible signal is produced from the loudspeaker
(or headphones) that is not so loud as to cause disturbance. The loudspeaker should be
capable of giving an output sound pressure level (SPL) exceeding 80 dB at 300 mm with the
gain control at maximum and a field strength at 1 kHz of –20 dB (400 mA/m).
A "press-to-listen" switch may be provided, which should be labelled as such. The amplifier
should not be overloaded by a field strength of 1 A/m or a corresponding loop current.
If a headphone output is provided, it should conform to the relevant provisions of IEC 61938.
10.2.5 If an audio signal output is provided for remote monitoring, the output should be
balanced and have a source impedance of less than 100 Ω.

– 8 – IEC 62489-1:2010/AMD1:2014
© IEC 2014
A status output, if required, to indicate failure of reception, should be in the form of an
isolated, normally closed, relay contact rated at 24 V d.c., 1 A. The threshold of detection for
such a circuit should be chosen so that it reliably detects a real fault in spite of any magnetic
interference that may be present, without false triggering, due, for example, to pauses in the
programme signal.
Any data connection is dependent on the system to which it is intended to be interfaced.
10.3 Recommendations for portable devices
Portable devices should conform to the following recommendations.
The recommendations of 10.2 for fixed devices should be followed, except that there is no
need for a provision for a loudspeaker, and an output for headphones is essential. This should
conform to the relevant provisions of IEC 61938. A battery condition check or "battery low"
indication should be provided.
An indication of magnetic field strength should also be provided, according to the
recommendations in Annex E of IEC 60118-4:2006.
Add, after Annex C, the following new Annexes D, E and F:

© IEC 2014
Annex D
(informative)
Neck loops
D.1 What is a neck loop?
A neck loop is a small induction loop, often about 230 mm diameter, worn as a 'necklace' by a
hearing-aid user. The neck loop may be fed, via a cable typically about 1 m long, from a
personal music player, a mobile phone or similar device, or a larger piece of audio equipment.
A neck loop may be electrically passive, i.e. comprise only one wire (but may have several
turns) and maybe a transformer, or active, including an amplifier or impedance converter and
a power source such as a battery. Neither type of neck loop uses a radio-frequency
technique, such as Near-Field Magnetic Induction (NFMI); the current in the loop is restricted
to audio frequencies.
D.2 Recommended construction
To prevent damage to the cable, or an unpleasant effect on the wearer, the cable or the loop
should be arranged to disconnect if the user moves in such a way as to apply tension to the
cable.
– 10 – IEC 62489-1:2010/AMD1:2014
© IEC 2014
Annex E
(normative)
Test jig for measuring the performance of neck loops

The test jig shall be entirely non-metallic (so a HATS is not suitable). The dimensions are
specified in the following figures.
IEC
IEC
Figure E.2 – Front view
Figure E.1 – Side view
IEC IEC
The loop passes between the back peg and the jig
Figure E.3 – Back view
body, outside the two upper front pegs and inside
the two lower front pegs. The lower part of the
loop can overhang the support, so as to resemble
the positioning when the loop is in use.
Figure E.4 – Arrangement of the neck
loop on the jig
© IEC 2014
Annex F
(normative)
Specifications for loop listeners and assistive listening devices (ALDs)

F.1 Loop listener
F.1.1 Sensitivity
A field strength of 400 mA/m at 1 kHz shall produce an output voltage of 150 mV across a
32 Ω resistive load.
F.1.2 Frequency response
The overall field-to-electrical output frequency response should approximate to the target
shown in Figure F.1. This is −3 dB at 350 Hz ± 50 Hz relative to the response at 1 kHz, with a
final gradient of 12 dB/octave and −3 dB (relative) at 10 kHz ± 1 kHz, with a final gradient of
6 dB/octave.
–3
–6
–9
–12
dB
–15
–18
–21
–24
–27
100 1 10
Hz KHz KHz
IEC
Figure F.1 – Target frequency response
This response is suitable for general use, but a second response may be provided for use
with headphones, including a high-frequency peak to improve intelligibility for users with
sensorineural impairment. The peak frequency should be approximately 3 kHz and the
response at the peak should be between +10 dB and +20 dB relative to the response at
1 kHz. The peak frequency and the relative level of the peak may be adjustable, preferably by
pre-set controls so as to avoid inadvertent adjustment.
NOTE Manufacturers are of course free to add other specified frequency responses.
F.1.3 Volume control
The volume control shall have a range of 40 dB ± 5 dB.
F.1.4 Total harmonic distortion
The total harmonic distortion, with a 32 Ω load and the volume control set at maximum gain,
shall not exceed 3 % at an output level 10 dB below 150 mV or the voltage corresponding to a
sound pressure level of 100 dB from the headphones.
F.1.5 Low-battery indicator
An indicator of low battery voltage shall be provided. The indication shall occur at a battery
voltage of (70 ± 5) % of the rated voltage of the battery.

– 12 – IEC 62489-1:2010/AMD1:2014
© IEC 2014
F.1.6 Connector
The connector for headphones shall be a 3,5 mm 3-contact jack conforming to IEC 60603-11.
F.2 Assistive listening device (ALD)
F.2.1 Sensitivity
With the AGC active and giving an output level 3 dB below the maximum output level, an input
of 50 dB SPL at 1 kHz shall produce an output voltage of 150 mV across a 32 Ω resistive
load, or an output of 100 dB SPL from headphones supplied with the product, when the
volume control is set to maximum.
F.2.2 Automatic gain control (AGC)
The AGC range shall be at least 25 dB for 6 dB change in output level. If the range is less
than 50 dB, a control and indicator shall be provided so that the input level of the AGC stage
can be set so as to activate the AGC.
NOTE This control is in addition to the volume control, which operates on the output of the AGC stage.
F.2.3 Frequency response
The overall sound-to-electrical output frequency response should approximate to the target
shown in Figure 1. This is -3 dB at 350 Hz ± 50 Hz relative to the response at 1 kHz, with a
final gradient of 12 dB/octave and -3 dB (relative) at 10 kHz ± 1 kHz, with a final gradient of
6 dB/octave.
This response is suitable for use with a neck loop but a second response may be provided for
use with headphones, including a high-frequency peak to improve intelligibility for users with
sensorineural impairment. The peak frequency should be approximately 3 kHz and the
response at the peak should be between +10 dB and +20 dB relative to the response at
1 kHz. The peak frequency and the relative level of the peak may be adjustable, preferably by
pre-set con
...