SIST EN ISO 20109:2025

SLOVENSKI STANDARD
01-november-2025
Nadomešča:
SIST EN ISO 20109:2017
Simultano tolmačenje - Oprema - Zahteve (ISO 20109:2025)
Simultaneous interpreting - Equipment - Requirements (ISO 20109:2025)
Simultandolmetschen - Ausstattung - Anforderungen (ISO 20109:2025)
Interprétation simultanée - Équipement - Exigences (ISO 20109:2025)
Ta slovenski standard je istoveten z: EN ISO 20109:2025
ICS:
91.040.10 Javne stavbe Public buildings
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 20109
EUROPEAN STANDARD
NORME EUROPÉENNE
June 2025
EUROPÄISCHE NORM
ICS 91.040.10 Supersedes EN ISO 20109:2016
English Version
Simultaneous interpreting - Equipment - Requirements
(ISO 20109:2025)
Interprétation simultanée - Équipement - Exigences Simultandolmetschen - Ausrüstung - Anforderungen
(ISO 20109:2025) (ISO 20109:2025)
This European Standard was approved by CEN on 10 May 2025.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 20109:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 20109:2025) has been prepared by Technical Committee ISO/TC 37 "Language
and terminology" in collaboration with CCMC.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by December 2025, and conflicting national standards
shall be withdrawn at the latest by December 2025.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 20109:2016.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 20109:2025 has been approved by CEN as EN ISO 20109:2025 without any modification.

International
Standard
ISO 20109
Second edition
Simultaneous interpreting —
2025-05
Equipment — Requirements
Interprétation simultanée — Équipement — Exigences
Reference number
ISO 20109:2025(en) © ISO 2025
ISO 20109:2025(en)
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
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Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 20109:2025(en)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Location of the parties in a communicative event . 4
4.1 General .4
4.2 Same room .5
4.3 Separate location .5
5 Generally applicable requirements . 5
5.1 Requirements relating to sound .5
5.1.1 General .5
5.1.2 Digital input and output . .5
5.1.3 Sound pressure level .5
5.1.4 Frequency response .6
5.1.5 Distortion .6
5.1.6 Noise and hum .7
5.1.7 Level consistency .7
5.1.8 Hearing protection .7
5.2 Requirements relating to image .7
5.2.1 Image quality .7
5.2.2 Synchronization of sound and image .7
6 Same room . 8
6.1 General .8
6.2 Latency .8
6.3 Video display .8
7 Separate location . 9
7.1 General .9
7.2 Latency .9
7.3 Video display .9
8 Interpreting equipment . 10
8.1 Interpreter interface .10
8.1.1 General .10
8.1.2 Hard console .10
8.1.3 Soft console .14
8.2 Microphones . 15
8.3 Interpreters’ headphones/headsets .16
8.3.1 Headphones .16
8.3.2 Headsets .17
8.4 Additional requirements related to signed language interpreting .17
8.4.1 Camera .17
8.4.2 Microphone.17
8.4.3 Background .17
8.4.4 Incoming image .17
8.4.5 Incoming sound .18
9 Interpreting system microphone behaviour .18
9.1 Interpreter microphone behaviour .18
9.2 Speaker microphone behaviour .18
9.3 Ambient microphone .18
10 Portable interpreting system . . 19
10.1 General .19

iii
ISO 20109:2025(en)
10.2 Microphones/transmitters .19
10.3 Receivers/transceivers .19
10.4 Transport system .19
Annex A (normative) Accessibility and usability of hard consoles .20
Annex B (normative) Requirements for the operation of a conference system .22
Annex C (normative) Measurement of hearing protection levels .23
Bibliography .25

iv
ISO 20109:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO’s adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 37, Language and terminology, Subcommittee
SC 5, Translation, interpreting and related technology, in collaboration with the European Committee
for Standardization (CEN) Technical Committee CEN/SS A07, Translation and Interpretation services, in
accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 20109:2016), which has been technically
revised.
The main changes are as follows:
— Clause 2 has been updated;
— two different situations regarding the location of the parties have been introduced;
— requirements relating to sound have been aligned with other standards and/or improved as to ensure
necessary sound quality transmitted to interpreters;
— detailed requirements for video displays have been added;
— specifications on interpreting system microphone behaviour have been added;
— a measurement method for the values pertaining to hearing protection has been added.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

v
ISO 20109:2025(en)
Introduction
This document specifies requirements for the equipment for simultaneous interpreting, as well as the quality
of sound and image transmitted to interpreters and from interpreters to the participants of a communicative
event. Technological progress has led to profound changes in how interpreters perform their services. They
can interpret in interpreting booths in the room in which the communicative event takes place, but either
the entire team of interpreters or part of it can also be working from an interpreting hub, or interpreters can
perform their services from an individual environment controlled by themselves. Different equipment can
be used in different situations to optimize performance. This document takes these different situations into
account.
Other relevant standards that can be applied in conjunction with this document, as required, are
ISO 17651 (all parts), ISO 22259 and ISO 24019.

vi
International Standard ISO 20109:2025(en)
Simultaneous interpreting — Equipment — Requirements
1 Scope
This document specifies requirements for the equipment needed for simultaneous interpreting and for the
quality of sound and image transmitted to interpreters and from interpreters to the audience, irrespective
of the place in relation to speakers, signers, the audience and other interpreters.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 639, Code for individual languages and language groups
ISO 9241-303, Ergonomics of human-system interaction — Part 303: Requirements for electronic visual displays
ISO 9241-410:2008/Amd 1:2012, Ergonomics of human-system interaction — Part 410: Design criteria for
physical input devices — Amendment 1
ISO 22259:2019, Conference systems — Equipment — Requirements
ISO 24019:2022, Simultaneous interpreting delivery platforms — Requirements and recommendations
ISO 24503, Ergonomics — Accessible design — Tactile dots and bars on consumer products
IEC 60268-1:2010, Sound system equipment — Part 1: General
IEC 60268-4, Sound system equipment — Part 4: Microphones
ITU-T P.58, Head and torso simulator for telephonometry
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
interpreter
person who interprets
[SOURCE: ISO 20539:2023, 3.1.13]
3.2
interpreting
interpretation
rendering spoken or signed information from a source language into a target language in spoken or signed
form, conveying both the meaning and language register of the source language content
[SOURCE: ISO 20539:2023, 3.1.11]

ISO 20109:2025(en)
3.3
simultaneous interpreting
mode of interpreting (3.2) performed while a speaker (3.5) or signer (3.6) is still speaking or signing
[SOURCE: ISO 20539:2023, 3.4.12]
3.4
signed language interpreting
interpreting (3.2) between two signed languages or between a signed language and a spoken language
[SOURCE: ISO 20539:2023, 3.4.3]
3.5
speaker
person addressing others using spoken language
[SOURCE: ISO 20539:2023, 3.4.5]
3.6
signer
person addressing others using signed language
[SOURCE: ISO 20539:2023, 3.4.6]
3.7
communicative event
encounter between two or more parties during which information is transmitted
[SOURCE: ISO 20539:2023, 3.4.32]
3.8
booth
simultaneous interpreting booth
self-contained unit enclosing the interpreter’s (3.1) workspace
Note 1 to entry: One of the purposes of booths is to provide insulation, both from the noise transmitted from the
booth’s external environment into the booth itself and vice versa, and from noise passing from one booth to another.
[SOURCE: ISO 20539:2023, 3.5.2.1]
3.9
interpreter interface
equipment containing controls used by the interpreter (3.1) to facilitate simultaneous interpreting (3.3)
EXAMPLE Controls for listening, viewing, speaking, signing.
[SOURCE: ISO 20539:2023, 3.5.2.8]
3.10
hard console
interpreter console
interpreter interface (3.9) containing physical controls for listening and speaking
[SOURCE: ISO 20539:2023, 3.5.2.9]
3.11
soft console
interpreter interface (3.9) which runs on a computer or portable IT device and has onscreen controls
[SOURCE: ISO 20539:2023, 3.5.2.10]

ISO 20109:2025(en)
3.12
microphone
transducer which converts sound into an electrical signal
[SOURCE: ISO 20539:2023, 3.5.2.30]
3.13
headphone
transducer which converts an electrical signal into sound, designed to be worn close to the ear
[SOURCE: ISO 20539:2023, 3.5.2.34]
3.14
headset
one or two headphones (3.13) combined with a microphone (3.12)
[SOURCE: ISO 20539:2023, 3.5.2.37]
3.15
video display
electronic device which represents information in a visual form
[SOURCE: ISO 20539:2023, 3.5.2.43]
3.16
interpreting system
combination of interpreting equipment and system for language distribution
Note 1 to entry: An interpreting system can require the use of booths (3.8) conforming to ISO 17651-1 or ISO 17651-2,
equipped with interpreter interfaces (3.9) conforming to this document, or a portable interpreting system (3.17)
conforming to this document.
[SOURCE: ISO 20539:2023, 3.5.2.27]
3.17
portable interpreting system
lightweight equipment with battery-operated components used in simultaneous interpreting (3.3) allowing
the interpreter (3.1) and participants (3.24) to move around
[SOURCE: ISO 20539:2023, 3.5.2.6]
3.18
simultaneous interpreting delivery platform
SIDP
virtual environment used in simultaneous interpreting (3.3) for managing the processing of audio and video
signals during the transmission of information from speakers (3.5) or signers (3.6) to distant interpreters
(3.1) and the interpreters’ renditions to a distant audience (3.25)
[SOURCE: ISO 20539:2023, 3.5.2.7]
3.19
relay interpreting
interpreting (3.2) in which the source language content is another interpreter’s (3.1) rendition
[SOURCE: ISO 20539:2023, 3.4.18]
3.20
relay status
indication of the source of an interpreter interface’s (3.9)incoming channel (3.22)
Note 1 to entry: The source can be the floor (3.21), direct interpreting (3.2), relay interpreting (3.19) or double relay
interpreting.
ISO 20109:2025(en)
[SOURCE: ISO 20539:2023, 3.5.2.16]
3.21
floor
audio output of conference system or simultaneous interpreting delivery platform (3.18) conveying auxiliary
input and input from microphones (3.12), excluding input originating from interpreters (3.1)interpreting (3.2)
from a spoken language
[SOURCE: ISO 20539:2023, 3.5.2.12]
3.22
incoming channel
electric circuit serving as a path for an audio or video signal to an interpreter interface (3.9)
[SOURCE: ISO 20539:2023, 3.5.2.13]
3.23
outgoing channel
electric circuit serving as a path for an audio or video signal from an interpreter’s (3.1)microphone (3.12) or
camera which, when activated by the interpreter, transmits the interpreter’s interpreting (3.2)
Note 1 to entry: Each language in which interpreting is provided at a conference is allocated an outgoing channel.
[SOURCE: ISO 20539:2023, 3.5.2.14]
3.24
participant
person who takes an active part in a communicative event (3.7)
[SOURCE: ISO 20539:2023, 3.4.33]
3.25
audience
group of listeners or spectators at a communicative event (3.7)
[SOURCE: ISO 20539:2023, 3.4.36]
4 Location of the parties in a communicative event
4.1 General
Parties in a communicative event can participate from the same room or from a separate location. Different
measures can be taken in order to provide the interpreter with the required audio-visual input, depending
on the location of the interpreter in relation to the speaker or signer, participant, other interpreters and
audience.
Technical requirements generally applicable for all situations are defined in Clause 5.
Technical requirements for situations in which the individual interpreter is in the same room as the speaker
or signer, participant, other interpreters and audience are defined in Clause 6.
Technical requirements for situations in which the individual interpreter is at a location separate to that of
one or more speakers or signers for the duration of their contributions or the entirety of the communicative
event are defined in Clause 7.
There can be individual interpreters in the same room or at a location separate to that of one or more
speakers or signers for the duration of their contributions or the entirety of the communicative event within
one and the same communicative event. Therefore, the applicable requirements and recommendations for
every individual interpreter shall be observed when applying the provisions of this document.

ISO 20109:2025(en)
4.2 Same room
The interpreter is in the same room as the speaker or signer, participant, other interpreters and audience.
The interpreting booths, whether they are permanent (see ISO 17651-1) or mobile (see ISO 17651-2), are in
the room in which the communicative event is taking place.
The interpreter has a direct view of the speaker or signer, audience and the room.
Latency is very short so that the delay between the direct sound from the room and the sound input in the
interpreter’s headphone cannot be perceived. See Clause 6.
4.3 Separate location
The interpreter is at a location separate to that of one or more speakers or signers, for the duration of their
contributions or the entirety of the communicative event, and views said speakers or signers contributing
from a separate location on a video display. The interpreter can also be at a location separate to that of one
or more other interpreters.
Where the interpreter is also separate to the audience, the interpreter views the audience on a video display.
Latency is less critical because the sound and image signals of the speaker can be synchronized before
reaching the interpreter. See Clause 7.
5 Generally applicable requirements
5.1 Requirements relating to sound
5.1.1 General
All audio signal processing shall be digital.
A conference system operated in combination with an interpreting system shall conform to Annex B.
5.1.2 Digital input and output
The interpreting system’s nominal digital input and output level shall be −30 dB .
FS
5.1.3 Sound pressure level
The nominal sound pressure level is referenced to a sinusoidal frequency of 1 kHz measured under free field
conditions, and shall result in an interpreting system’s level of −30 dB . Sound pressure levels shall conform
FS
to Table 1.
ISO 20109:2025(en)
Table 1 — Sound pressure level
Sound pressure level Nominal (at −30 dB ) Upper minimum value Unit
FS
at the speaker’s microphone
housing/capsule, for micro-
75 ≥105 dB
SPL
phones with an intended
speaking distance > 15 cm
at the speaker’s microphone
housing/capsule, for micro-
85 ≥ 115 dB
SPL
phones with an intended
speaking distance ≤ 15 cm
at the interpreter’s micro-
phone housing/capsule,
for microphones with an 75 ≥ 105 dB
SPL
intended speaking
distance > 10 cm
at the interpreter’s micro-
phone housing/capsule,
for microphones with an 85 ≥ 115 dB
SPL
intended speaking
distance ≤ 10 cm
5.1.4 Frequency response
The interpreting system excluding the microphones and headphones shall correctly reproduce audio-
frequencies between 125 Hz and 15 000 Hz, with a variation of maximum ±1 dB. For frequencies higher
than 15 000 Hz, the frequency response shall not exceed +1 dB. Additionally, the interpreting system shall
apply a high-pass filter attenuating the frequencies below 125 Hz with a slope of at least 12 dB/oct in order
to improve speech intelligibility. See Figure 1.
Key
X Hz
Y dB
Figure 1 — Frequency response
5.1.5 Distortion
The interpreting system shall be free of any perceptible audio distortion.
The interpreting system shall exhibit a total harmonic distortion (THD) level below 1 % at any level up to
0 dB at 1 kHz.
FS
ISO 20109:2025(en)
5.1.6 Noise and hum
The interpreting system shall not introduce any perceptible noise or hum to the audio signal. The interpreting
system, excluding microphone and headphones, shall have a signal-to-noise ratio (SNR) of at least 100 dB.
A microphone, with an intended speaking distance of 10 cm or less used by the interpreter or 15 cm or less
used by the speaker for capturing the source signal, including the analogue to digital converter, shall exhibit
an SNR of at least 65 dB at a sound pressure level of 94 dB at 1 kHz at the microphone housing/capsule.
SPL
A microphone, with an intended speaking distance of more than 10 cm used by the interpreter or more than
15 cm used by the speaker for capturing the source signal, including the analogue to digital converter, shall
exhibit an SNR of at least 70 dB at a sound pressure level of 94 dB SPL at 1 kHz at the microphone housing/
capsule.
5.1.7 Level consistency
All audio signals should be automatically adjusted to minimize the audio level difference between
interpreters as well as between the interpreter and the floor, assuming that the input level varies between
nominal and ±12 dB. The variation of the output level of the interpreting system shall be no more than ±3 dB
for each distributed interpreted language channel and distributed floor channel at an input level of
−30 dB ± 12 dB.
FS
5.1.8 Hearing protection
To avoid damaging the hearing of the interpreter, equipment providing protection against harmful sound
levels and acoustic shock being transmitted to their ears shall be used.
NOTE Protection can be provided by the interpreter interface in combination with headphones or headsets.
A visual hearing-damage warning shall be shown when the average sound pressure level is higher than
80 dBA within 60 s, in accordance with Clause C.4. The warning shall be repeated within 60 s when the
SPL
average value continues to be higher than 80 dBA
SPL.
Loud sounds shall be limited to a maximum output level of 94 dBA for any duration longer than 100 ms.
SPL
The acoustic level transmitted to the ears shall not be more than 100 dBA after the settling time as
SPL,
defined in Annex C.
For a method to measure these values, see Annex C.
5.2 Requirements relating to image
5.2.1 Image quality
The quality of the image transmitted shall be such that it prevents image noise or any other visible distortions
such as blurring or freezing.
NOTE A resolution of 1 920 × 1 080 (1 080 p) at a rate of 30 frames per second (fps) is commonly used.
5.2.2 Synchronization of sound and image
Images provided to the interpreter on individual displays, as well as shown on centrally placed displays,
shall be synchronized with sound so as to provide lip synchronization. This means that the image shall
neither lag sound by more than 125 ms nor shall it lead it by more than 45 ms. ITU-R BT.1359 addresses
sound and image synchronization.

ISO 20109:2025(en)
6 Same room
6.1 General
All components of an interpreting system should be interconnected by wire.
The interpreter should use a hard console, which shall conform to 8.1.2.
NOTE 1 A wired system is less prone to disruptions.
NOTE 2 According to the classification level set out by the client for a specific communicative event, it can be
necessary to keep information confidential and uncorrupted. For the different classification levels, see ISO/IEC 27001.
Legal requirements can apply.
6.2 Latency
The overall delay of the video images from the speaker to the interpreter’s video display shall not exceed 125 ms.
The time between the microphone button press and the microphone ON/OFF state change shall not
exceed 250 ms.
The input and/or output shall become active within 250 ms after the input and/or output has been changed.
If no video displays are used or the soundproofing of the interpreter’s working environment is such that
the interpreter can hear the sound coming from the room in which the communicative event takes place
and/or the sound coming from other interpreters, the delay between the time the direct sound arrives at
the interpreter’s ear and the corresponding sound received by the interpreter through the interpreter's
headphones shall not exceed 10 ms.
6.3 Video display
Video displays in or in front of the booth facilitate the interpreter’s view of speakers and signers in large
rooms in which communicative events take place, especially the speaker’s or signer’s facial expressions and
lip and hand movements. They also bring presentations closer to the interpreter. When video displays are
available, they shall offer views of the speaker/signer and the presentation. Video displays should also offer
the room overview and a combined image of the speaker and the presentation.
Video displays shall be used if one or more of the following conditions are met:
— The interpreter does not have a direct view of the speaker or signer and therefore cannot discern their
facial expressions and lip and hand movements. Spontaneous off-screen comments or questions from
others than the main speakers may be allowed.
— The speaker or signer is distant.
— The speaker at the rostrum or the projection screen is more than 20 m away.
— The signer at the rostrum is more than 6 m away.
— The lighting of the speaker’s rostrum does not allow the interpreter to discern their lip and hand
movements.
— The distance between the booths and the projection screen is at least three times the projection screen’s
diagonal.
— The angle of the interpreter’s visual line towards the projection screen is less than 35°.
— The booths are located behind the main speakers or at a higher level.
When such a video display is provided, it shall be positioned at a convenient ergonomic angle, i.e. with a
gaze angle from 0° to 40° and a head-tilt angle from 0° to 25° in accordance with ISO 9241-303. Its diagonal
shall be proportional to the viewing distance. The incoming signal shall be displayed without distorting its
original aspect ratio.
ISO 20109:2025(en)
It shall not impede visibility from inside the booth into the room in which the communicative event takes
place, nor shall it encroach on leg room.
NOTE Good results have been achieved with video displays inside a permanent booth with a diagonal dimension
between 25 cm (15 inches) and 43 cm (22 inches) for one interpreter, or between 38 cm (15 inches) and 43 cm (17
inches) if shared between two interpreters. In settings with mobile booths, good results have been achieved with
placing screens outside the booth, to avoid excessive clutter on the limited work surface inside the booth.
Video displays shall be flat and flicker-free. They should be anti-glare and easily cleanable.
7 Separate location
7.1 General
Where a conference system conforming to ISO 22259 is not available, a solution conforming to ISO 24019
shall be used to connect the distant interpreter, speaker or signer to the communicative event.
The interpreter may use a hard console (see 8.1.2) or a soft console (see 8.1.3).
NOTE 1 A local on-premises system is less prone to disruptions due to not using external network connections and
better management of audio transmitted to interpreters.
NOTE 2 According to the classification level set out by the client for a specific communicative event, it can be
necessary to keep information confidential and uncorrupted. For the different classification levels, see ISO/IEC 27001.
Legal requirements can apply.
7.2 Latency
The overall delay between the speaker’s and interpreter’s sound and the interpreter’s ear shall not
exceed 500 ms.
The overall delay of the video images from the speaker to the interpreter’s video display shall not exceed 500 ms.
The time between the microphone button press and the microphone ON/OFF state change should be
maximum 250 ms. It shall never exceed 500 ms.
For requirements on the synchronization of image and sound, see 5.2.2.
7.3 Video display
An image of any speaker or signer communicating at the communicative event, as well as any slides or other
content projected live to the participants or the audience, shall be made available to the interpreter. The
incoming signal shall be displayed without distorting its original aspect ratio.
When the interpreter uses a soft console, slides and other materials should be displayed in a separate
window. The interpreter shall be able to adjust the size and placement of the individual windows.
The quality of the image transmitted to the interpreter shall be such that it prevents visible distortions such
as blurring or freezing.
In cases where there is a distant speaker or signer, the interpreter shall be provided with an image of the
speaker or signer, as well as any slides or other content available.
The interpreter shall be provided with an overview of the room or rooms in which the communicative event
takes place.
ISO 20109:2025(en)
8 Interpreting equipment
8.1 Interpreter interface
8.1.1 General
There shall be one interface for each interpreter.
8.1.2 Hard console
8.1.2.1 General
The hard console may be either free-standing on or integrated into the working surface. Reflections of its
surface shall not impede visibility.
It shall be possible to quickly and easily service or replace a malfunctioning console or its microphone
without impairing the functioning of the rest of the system.
The hard console shall be accessible and usable in accordance with Annex A.
8.1.2.2 Headphones/headset connector
In order to conform to the latency specified in 6.2 and hearing protection specified in 5.1.8, each hard console
shall have one non-locking, 3,5 mm headphones/headset connector socket on both the left and the right side.
Each 3,5 mm connector shall follow the TRRS (tip/ring/ring/sleeve) CTIA/AHJ (Cellular Telecommunications
and Internet Association/American Headset Jack) standard, where:
— 1 connects to headphone left;
— 2 connects to headphone right;
— 3 connects to ground;
— 4 connects to microphone.
See Figure 2.
Figure 2 — 3,5 mm TRRS connector pinning
When a headset is connected, the console’s fixed microphone shall remain activated, as well as the
microphone on-air indicator light. The headset microphone may be activated manua
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