ISO/DIS 17651-4

ISO/TC 37/SC 5

Secretariat: DIN

Date: 2025-11-06

Simultaneous interpreting — Interpreters’ working environment —

Part 4:
Requirements and recommendations for signed language interpreting

DIS stage

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Contents

Foreword iv

Introduction v

1 Scope 1

2 Normative references 1

3 Terms and definitions 2

4 General requirements 3

4.1 Workspaces 3

4.2 Siting & visibility 4

4.3 Accessibility 4

4.4 Technical control and technical support staff 5

4.5 Support services 6

4.6 Fire safety and evacuation 6

5 Equipment for all workspaces 6

5.1 Lighting 6

5.2 Backdrop 6

5.3 Visual display 6

5.4 Camera and pre-sets 7

5.5 Incoming sound 8

5.6 Whiteboard 8

6 On the floor 8

6.1 Allocation of workspaces 8

6.2 Meeting hall 8

6.3 Conference hall 9

7 Signed language interpreting booth 14

7.1 General requirements 14

7.2 Dimensions 15

7.3 Interpreter's view and placement 17

7.4 Booth interior 18

8 From a hub 20

8.1 General requirements 20

8.2 Interpreter's view 20

9 Amenities for interpreters 20

9.1 Toilets 20

9.2 Interpreters' room 20

Annex A (informative) Simplified checklists 21

Annex B (informative) Flowchart 22

Annex C (informative) Workspace placements in meeting halls 23

Annex D (informative) Workspace placements in conference halls 24

Annex E (informative) Layout of visual displays 28

Annex F (informative) Broadcast image 33

Bibliography 36

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 documents 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).

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.

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This document was prepared by Technical Committee ISO/TC 37, Language and terminology, Subcommittee SC 5, Translation, Interpreting and related technology. The ISO/IEC Guide 71:2014 is used to develop an accessible standard in consultation with key stakeholders.

A list of all parts in the ISO 17651 series can be found on the ISO website.

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.

Introduction

This document concerns the logistical and technical equipment requirements and recommendations for the working environment of signed language interpreters.

Interpreting services can be provided at a communicative event where the interpreter is at the same or a different location as speakers, signers, participants, the audience, or other interpreters. In both cases technical support is needed. Signed and spoken language interpreters interpreting at the same communicative event interact and collaborate with each other. As signed languages are expressed and perceived in the visual-manual modality, interpreting into and from a signed language requires a working environment that facilitates this. Measures need to be taken to provide the signed language interpreter with the required audio-visual input, and an unobstructed view of the communicative event, depending on the location of the interpreter in relation to the speaker or signer, participant, audience and other interpreters.

Signed language interpreters interpret in various workspaces, depending on:

• the type of setting such as conference interpreting (ISO 23155^[1]), community interpreting (ISO 13611^[2]), healthcare interpreting (ISO 21998^[3]), legal interpreting (ISO 20228^[4]);
• the layout of the room where the communicative event takes place, such as
• either a dedicated signed language interpreting booth, a dedicated workspace for signed language interpreting on the floor, or both
• or at a distance from a signed language interpreting booth in an interpreting hub.

This document addresses the following:

1. workspace requirements specific to signed language interpreters;
2. visual communication between interpreters and participants at an event;
3. teamwork among interpreters and among interpreters and technical support staff;
4. technical requirements and dedicated technical support;
5. dimensions and design of a dedicated signed language interpreting booth;
6. a working environment that minimises factors contributing to cognitive load, recognising that interpreting demands sustained high levels of concentration.

This document complements the existing Parts (1-3) of the ISO 17651 series; these set out the essential requirements for simultaneous interpreting: Part 1: Requirements and recommendations for permanent booths, Part 2: Requirements and recommendations for mobile booths, Part 3: Requirements and recommendations for interpreting hubs and this fourth part details comprehensively the relevant requirements for the workspaces of signed language interpreters.

Simultaneous interpreting — Interpreters’ working environment —

Part 4:
Requirements and recommendations for signed language interpreting

This document specifies the logistical and technical equipment requirements and recommendations for the working environments of signed language interpreters. This document also ensures the usability and accessibility of workspaces of signed language interpreters.

It draws from, and adds to, the existing standards on interpreters’ working environment, interpreting equipment, simultaneous interpreting delivery platforms and conference equipment ISO 17651-1^[5], ISO 17651-2^[6], ISO/FDIS 17651-3^[7], ISO 20109^[8], ISO 24019^[9] and ISO 22259^[10].

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 9241-20, Ergonomics of human-system interaction — Part 20: An ergonomic approach to accessibility within the ISO 9241 series

ISO 9241-303, Ergonomics of human-system interaction — Part 303: Requirements for electronic visual displays

ISO 9241-303:2011, Ergonomics of human-system interaction — Part 303: Requirements for electronic visual displays

ISO 17069:2020, Accessible design — Consideration and assistive products for accessible meeting

ISO 17069, Accessible design — Consideration and assistive products for accessible meeting

ISO 17651-1, Simultaneous interpreting — Interpreters’ working environment — Part 1: Requirements and recommendations for permanent booths

ISO 17651-1:2024, Simultaneous interpreting — Interpreters’ working environment — Part 1: Requirements and recommendations for permanent booths

ISO/FDIS 17651-3, Simultaneous interpreting — Interpreters’ working environment — Part 3: Requirements and recommendations for interpreting hubs

ISO 20109:2025, Simultaneous interpreting — Equipment — Requirements

ISO 20109, Simultaneous interpreting — Equipment — Requirements

ISO 21542:2021, Building construction — Accessibility and usability of the built environment

ISO 21542, Building construction — Accessibility and usability of the built environment

ISO 22259:2019, Conference systems — Equipment — Requirements

ISO 24019, Simultaneous interpreting delivery platforms — Requirements and recommendations

ISO 24019:2022, Simultaneous interpreting delivery platforms — Requirements and recommendations

ISO 24019:2022, Simultaneous interpreting delivery platforms — Requirements and recommendations

IEC 60118-4, Electroacoustics - Hearing aids - Part 4: Induction-loop systems for hearing aid purposes - System performance requirements

IEC 60268-4:2018, Sound system equipment - Part 4: Microphones

IEC 62489-1, Electroacoustics - Audio-frequency induction loop systems for assisted hearing - Part 1: Methods of measuring and specifying the performance of system components

EN ISO 22259:2021, Conference systems - Equipment - Requirements (ISO 22259:2019)

EN 1335-1, Office furniture - Office work chair - Part 1: Dimensions - Determination of dimensions

For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

• ISO Online browsing platform: available at http://www.iso.org/obp
• IEC Electropedia: available at http://www.electropedia.org/

interpreter

person who interprets

[SOURCE: ISO 20539:2023^[11], 3.1.13]

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^[11], 3.1.11]

signed language

language which uses a combination of hand shapes, orientation and movement of the hands, arms or body, and facial expressions

[SOURCE: ISO 20539:2023^[11], 3.1.7]

signed language interpreting

interpreting (3.2) between two signed languages (3.3) or between a signed language and a spoken language

[SOURCE: ISO 20539:2023^[11], 3.4.3]

simultaneous interpreting

mode of interpreting (3.2) performed while a speaker or signer is still speaking or signing

[SOURCE: ISO 20539:2023^[11], 3.4.12]

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^[11], 3.5.2.1]

video display

electronic device which represents information in a visual form

[SOURCE: ISO 20539:2023^[11], 3.5.2.43]

overlay

substitution of part of an image by another image

[SOURCE: ISO 20539:2023^[11], 3.5.2.44]

accessibility

extent to which products, systems, services, environments and facilities can be used by people from a population with the widest range

[SOURCE: ISO 9241-112:2025^[12], 3.11, modified - "of user needs, characteristics and capabilities to achieve identified goals in identified contexts of use" deleted at the end of the definition; Note 1 to entry deleted]

communicative event

encounter between two or more parties during which information is transmitted

[SOURCE: ISO 20539:2023^[11], 3.4.32]

Signed language interpreters interpret in diverse settings based on the nature and configuration of each communicative event. All workspaces shall provide adequate conditions, including:

• uninterrupted incoming sound;
• clear lighting;
• unobstructed view of the room and the visual resources;
• physical comfort.

Appropriate logistical and technical arrangements shall be made to meet the above requirements.

Workspaces for signed language interpreters can be:

• a dedicated space on the floor where the communicative event is held;
• a signed language interpreting booth at the venue where the communicative event is held;
• a signed language interpreting booth in an interpreting hub.

When providing signed language interpreting services at a communicative event, organisers and service providers shall ensure accessibility support in accordance with ISO 17069.

The logistical and technical setup shall enable all signed and spoken language interpreters at the same communicative event to collaborate with each other from their respective workspaces.

When designing new rooms or renovating existing ones, workspaces for interpreters — either a booth, a workspace on the floor, or both — shall be integrated into the structure so that the room itself and the workspaces and interpreting booths constitute a well-balanced unit in terms of layout, people flow within buildings, accessibility and usability in accordance with ISO 21542.

Workspaces for interpreters in a shared physical space with participants shall be clearly visible, free of visual obstructions (see 4.2) and located away from extraneous sources of disturbance, such as kitchens, public corridors and passageways. The workspaces shall not be placed in front of a window or an area that produces a bright backlight.

In order to facilitate speech intelligibility, the room should not cause reverberation or echoes exceeding the values recommended for the type of room in accordance with AS/NZS 2107^[13].

NOTE AS/NZS 2107^[13] also specifies methods of measuring the background sound level and the reverberation time in unoccupied spaces.

Technical advisors and spoken or signed language interpreters with expert knowledge of workspaces for interpreters and related equipment, qualified technicians or suppliers shall be consulted for the design and operation.

Signed language interpretation involves visual interaction with signing participants. When signers are present, signed to spoken language interpretation shall be provided from the interpreter workspace on the floor where the communicative event is held (4.1). Additionally, a second signed language interpreting team can provide interpretation into a signed language from a dedicated sign language interpreting booth (Clause 7). The signed language interpretation can be broadcast to either screens in the same hall and venue, or publicly, or both.

Visual cooperation between the interpreters in the signed language interpreting team(s) is essential for teamwork; therefore there shall be no visual obstructions between the lines of sight of the interpreters, speakers, signers, participants, the audience, or other interpreters, nor between the workspaces of the interpreting teams.

It shall be possible to quickly, easily and safely access:

• the dedicated signed language interpreting workspaces on the floor;
• one booth from another booth;
• all booths from inside or outside the room.

A minimum of 10 % of the booths, rounded up to the next whole number, shall be accessible to persons with a disability, in accordance with ISO 21542.

An individual induction loop shall be installed in the room and the dedicated signed language interpreting booth, and shall comply with IEC 60118-4 and IEC 62489-1.

Live captions provide access to the spoken language in text format and should be provided when requested by the interpreters.

In settings where technical equipment for signed language interpreters is used, specifically trained technical support staff shall assist and monitor the interpreter's work system (see ISO 6385^[14]) to:

• check the set-up of the dedicated interpreting workspaces, including the required equipment such as cameras, lighting, backdrop, audio and audio receivers (see 7.4);
• align the dedicated lighting on the interpreter to the light in the room (see 5.1 and 7.4.2.2);
• demarcate and block off the dedicated interpreting workspace on the floor, for example with the use of a stanchion;
• adjust or pre-set the height, zoom and framing of the camera for each of the interpreting team members;
• demonstrate and explain to the interpreting team the use of a pre-set camera control panel, if provided (see 7.4.2.5);
• send the input to the broadcasters to display the broadcast image of the signed language interpreter, such as on television, webcast and app streaming.

The technical controls shall be placed close to the interpreting workspaces so that:

• technical support staff can access them easily;
• visual communication between the technical support staff and the interpreters is possible;
• technical support staff have a clear view of the entire room, including the rostrum, speakers, signers and all visual aids such as projection screens and displays.

The technical control should be installed:

• on a table;
• in a rack;
• or in a booth that conforms to the requirements and recommendations for a permanent booth or a mobile booth for simultaneous interpreting in accordance with ISO 17651-1^[5] or ISO 17651-2^[6].

If not present in the room, a central technical control shall be available in the venue.

Interpreters shall be able to communicate directly with the technical support staff, who shall have safe, quick, and easy access to the interpreter workspaces and the room.

NOTE In technically complex settings it has proven to be useful to have the presence of dedicated technical support staff for the signed language interpreting team.

Signed language interpreters are unable to hold and handle documents whilst interpreting into a signed language. Consequently, to conduct the required preparation, the event organizers shall provide signed language interpreters with all relevant documentation prior to the start of the event.

Fire safety evacuation maps and plans shall be available on the workspaces on the floor (see Clause 6), inside the dedicated booth (see Clause 7) and inside the interpreters' room (see 9.2).

To protect the interpreter from disability glare (see ISO 9241-303:2011^[15], 5.4.11), indirect lighting, or a lamp reflector shall be used. Each lighting source projected on the interpreter shall be individually and manually adjustable for:

• beam angle;
• light intensity.

The backdrop behind the signed language interpreter shall cover the vertical space from the floor up. The horizontal space shall comfortably cover the signing space of the interpreter. The following minimum dimensions shall apply:

• width: 2,00 m;
• height: 2,30 m.

The location where the interpreter will be positioned shall be marked on the floor. The distance between the interpreter and the backdrop shall be at least 1 metre.

The backdrop shall have a uniform colour, so that the image of the interpreter can be seen without any visual distraction. The backdrop colour value shall be mid-range. The backdrop material shall be flat without any unevenness, non-glaring, and cause no reflections.

NOTE Viewers who identify as deafblind or with a visual impairment should be consulted to determine if a specific colour backdrop is preferred; interpreters should wear plain clothes in a colour that contrasts with their skin colour.

A video display in the direct line-of-sight of the interpreter shall provide the incoming images as seen by the audience on the main screen. The video display 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.

For interpreters who are working directly from captions, a second video display shall provide the live text and shall be positioned underneath or next to the camera to avoid eye strain. The video display shall be positioned at a convenient ergonomic angle for the interpreter to read the text without the need to tilt or move their head.

The incoming signal of the video displays shall be displayed without distorting their original aspect ratio. Video displays shall be flat and flicker-free. They should be anti-glare and easily cleanable. The video display shall not obstruct visibility into and from the room in which the communicative event takes place.

Screen sizes shall be in proportion to the viewing distance to ensure the interpreter can comfortably read any displayed text. There shall be sufficient contrast between the text and the background. Both the symbols and the screen background should have different luminance or colour, in accordance with ISO 9241-303^[16].

The incoming image shall follow the requirements in accordance with ISO 20109:2025, 5.2. Video displays shall conform to ISO 20109:2025, 7.3.

The image size and quality shall be such that the visual content is readable and the speaker’s face is clearly visible. The image of the signer shall transmit their detailed facial expression, lip and hand movements. The image of the signer shall be framed from one hand span above their head to just below their hips so that the hands of the signer are never out of frame. Examples of different configurations on the visual display are provided in Annex E.

NOTE 1 Good results have been achieved with:

• dual video displays with a diagonal dimension between 140 cm (55 inches) and 165 cm (65 inches) at a viewing distance of between 170 cm and 200 cm;
• single video displays with a diagonal dimension between 165 cm (65 inches) and 216 cm (85 inches) with multi-view of the different video signals at a viewing distance of between 170 cm and 200 cm.

NOTE 2 It is good practice that technical support staff and interpreters coordinate the configuration of the content to be displayed to interpreters.

The camera shall be positioned at the eye level of the interpreter 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.

The camera height shall be adjustable via a control panel automatically adapting the pre-set height of the camera to the height of the interpreter. Specifically trained technical support staff shall be available to set the camera and program any pre-sets (see 4.4).

The broadcast image of the interpreter shall:

• position the interpreter within the frame with sufficient space on either side to fully capture arm movements;
• transmit the interpreter's detailed facial expression, lip movements, and hand movements;
• be framed at least 15 centimetres above the interpreter's head to just below their hips so that the interpreter’s hands are never out of frame;
• cover at least 1/3 of the horizontal plane of the display on the main screen in the room;
• not be overlayed by any other images or text.

Examples of broadcast images are provided in Annex F.

The camera shall have a frame rate of 30 (FPS) or higher to capture the fluid movements in signed language communication, including facial expressions and mouth movements. For viewers, a lower resolution with adequate bitrate provides better signed language comprehension than a higher resolution with insufficient bitrate ^[17][18].

The minimum bitrates for various resolutions are:

3840×2160 (4K): 16 Mbps

1920×1080 (Full HD): 8 Mbps

1280×720 (HD): 4 Mbps

In case of bandwidth constraints, the encoder shall maintain an adequate bitrate, reducing spatial resolution as necessary, and the compression quality shall take precedence over high spatial resolution.

Incoming sound shall be provided through a wireless receiver in accordance with ISO 20109:2025, 10.3, and shall be connected to each interpreter’s headphones, allowing for uninterrupted sound input.

NOTE Good results have been achieved with Radio Frequency (RF) receivers. Infrared (IR) receivers are not suitable as the interpreters' signing movements disrupt the infrared signal.

The receiver shall allow the interpreters to select either the audio from the floor or a minimum of three pre-set interpreted languages.

The interpreters' headphones shall conform to ISO 20109:2025, 8.3.1.

A whiteboard of A4 size with markers and wiper shall be provided for the interpreters to write information on.

The allocation of the interpreters' workspace depends on the layout of the meeting hall or conference hall and the seating arrangement of the various parties in the communicative event (see ISO 22259^[10]).

NOTE It is good practice that event organizers consult with the signing participants and interpreters on the location of the interpreters’ workspace and the participants’ seating arrangements.

The interpreters' workspace(s) shall be placed in such a way that the interpreters have a direct view of the entire room, the speakers, signers and all visual resources, such as projection screens and displays.

In a meeting hall where all parties are physically present there are various possible workspaces. Examples of workspaces in meeting halls are provided in Annex C. The workspace shall be allocated across from the signing audience members at a maximum distance of 3 metres.

In case the workspace does not provide the visibility, lighting or sound levels for interpreters to interpret, the following shall be provided:

• lighting in accordance with 5.1;
• incoming sound in accordance with 6.3.6.5;
• a microphone in accordance with 6.3.6.7;
• visual displays in accordance with 5.3.

In a small meeting hall where all audience members are seated, the interpreters shall also be seated on comfortable chairs in accordance with EN 1335-1 with the following characteristics:

• easily movable;
• adjustable height;
• adjustable or removable armrests.

Signed language interpretation involves visual interaction with signing participants. When signers are present, signed to spoken language interpretation shall be provided from the interpreters' workspace on the floor (Clause 6). Additionally, a second signed language interpreting team can provide interpretation into a signed language from a dedicated signed language interpreting booth (Clause 7). The signed language interpretation can be broadcast to either screens in the same hall and venue, or publicly, or both.

The interpreters' workspaces shall be placed in such a way that the interpreters have a direct view of the entire room, including the rostrum, speakers, signers and all visual aids, such as projection screen and displays (see Annex D). The interpreting workspaces shall be situated in such a way that the interpreters’ view is without any visual obstruction. The sign language interpreters’ workspaces shall not hinder the view of the spoken language interpreters' booths into the room. In large rooms video displays shall be used to facilitate the interpreters' view of speakers and signers, in accordance with ISO 20109.

In a hall with a theatre-style seating arrangement, there are two dedicated workspaces for signed language interpreters:

• on the floor, next to the rostrum, facing the audience (see 6.3.4);
• on the floor, facing the rostrum (see 6.3.5).

A designated area next to the rostrum facing the rostrum shall be allocated for signed language interpreters, within view of all participants in the audience and without any visual obstructions (Figure 1).

A second space at the front of the room, facing the rostrum, shall be allocated for the team of interpreters providing interpreting services between a signed and a spoken language or between two signed languages (Figure 2).

In a communicative event, both workspaces can be used at the same time to provide interpreting services: the workspace on the conference hall floor next to the rostrum facing the audience for signing audience members and the workspace on the conference floor facing the rostrum for signers on the rostrum. When signing participants are physically present at the communicative event, the dedicated interpreting workspace on the conference hall floor facing the rostrum shall be used to provide interpretation into a spoken language for signers on the rostrum (Figure 2).

Additionally, in case the conference hall has a dedicated booth (Clause 7) a second team can provide interpretation into a signed language from the booth for the image to be broadcast (Annex F).

For each additional signed language, additional dedicated workspaces shall be provided next to (Figure 3) and opposite of the rostrum (Figure 4). If available, additional dedicated signed language interpreting booths can also be used for each additional signed language (Clause 7).

Additional examples of placement of workspaces in a conference hall are provided in Annex D.

Figure 1 — Dedicated workspaces for interpreters on the floor of a conference hall next to the rostrum (from a spoken language to one signed language), with a speaker at the rostrum

Figure 2 — Dedicated workspaces for interpreters on the floor of a conference hall: next to the rostrum (from a spoken to a signed language) and facing the rostrum (from a signed to a spoken language), with a signer at the rostrum

Figure 3 — Dedicated workspaces for interpreters on the floor of a conference hall next to the rostrum (from spoken language(s) into two signed languages), with a speaker at the rostrum

Figure 4 — Dedicated workspaces for interpreters on the floor of a conference hall: next to the rostrum (from spoken language(s) into two signed languages) and facing the rostrum (from a signed to a spoken language), with a signer at the rostrum

The main signed language interpreting workspace shall be positioned next to the rostrum to allow for a view of the rostrum and the signers and speakers, as well as visual contact between the interpreters and physically present signing audience members (, Figure 3). The allocated workspace shall be at least 2 x 2 metres and clearly demarcated and designed to prevent any non-interpreter from physically entering the space, for example, with the use of stanchions. A video display (see 5.3) shall be used to provide the audience-facing interpreter with a view of the speaker or signer, as well as other visual materials displayed on the main screen for the audience.

A second signed language interpreting workspace shall be positioned across from the audience-facing interpreter to allow for visual contact and cooperation between the interpreters (Figure 2, Figure 4). This workspace can also be used to provide interpretation to signers on the rostrum. The allocated workspace shall be clearly marked to avoid any non-interpreter physically entering the workspace.

General

The workspace shall have:

• lighting in accordance with 5.1 and 6.3.6.2;
• a backdrop in accordance with 5.2 and 6.3.6.3;
• visual display(s) in accordance with 5.3 and 6.3.6.4;
• a camera in accordance with 5.4 and 6.3.6.6;
• incoming sound in accordance with 5.5 and 6.3.6.5;
• a microphone in accordance with 6.3.6.7.

Lighting

Lighting shall be provided in accordance with 5.1.

Additional lighting sources shall be used to ensure a clear image of the interpreter without shadows on the interpreter’s body, hands, face or the backdrop. The interpreter in the second workspace, opposite of the rostrum, shall be clearly visible to the interpreter next to the rostrum.

Backdrop

A backdrop shall be set up on the rostrum behind the interpreter (Figure 3). The backdrop shall meet the specifications in 5.2. The backdrop shall be portable.

Visual display

A video display shall provide the incoming images in accordance with 5.3.

Incoming sound

The incoming sound shall be provided in accordance with 5.5.

In communicative events where only one spoken language is used, an audio feedback monitor can be used as the audio source for each interpreting team. The audio feedback monitor shall be placed in front of the interpreter at a maximum distance of 2 metres and project the audio directly towards the interpreter. The monitor should have a manual control for the interpreters to individually adjust the volume.

Camera

In circumstances when the image of the interpreter needs to be displayed for the audience on the main conference hall screen or be streamed on the internet, a dedicated camera shall capture the image of the interpreter (5.4).

The camera can be a built-in camera in the room or a stand-alone camera that is purposely set up.

Microphone

The interpreters' microphone shall be wireless, handheld, in accordance with ISO 20109:2025, 8.2 and 10.2. The microphone shall be intended for close-talking use (IEC 60268-4:2018). The microphone shall be directly managed by the interpreters and not centrally managed, nor shall it be part of the participants’ request to speak or queue mode. In accordance with ISO 22259:2019^[19], Annex D, the microphone should either be:

1. In press and release mode: the microphone is switched ON by pressing the microphone button. If the microphone is already ON it will be switched OFF.
2. Push-to-talk mode: the microphone is switched ON by holding the microphone button. Releasing the button switches the microphone OFF.

The signed language interpreting booth(s) for signed language interpreting shall be positioned close to, and not separated from, the spoken language interpreting booth(s) to facilitate collaboration, visual contact, as well as cabling, between them.

The signed language interpreting booth is dedicated to and designed for providing interpretation into a signed language. This interpretation shall be broadcast or displayed on a screen in the room.

NOTE A spoken language interpreting booth temporarily converted for signed language interpreting purposes cannot be considered a signed language interpreting booth.

A signed language interpreting booth shall comfortably accommodate a team of three interpreters, allowing them to collaborate effectively. To allow for sufficient space for the interpreting team and the specific signed language interpreting equipment, the booth dimensions shall be larger than the spoken language interpreting booth as per ISO 17651-1. The dimensions of the signed language interpreting booth are specified in 7.2.

A dedicated booth shall have:

• doors in accordance with ISO 17651-1:2024, 5.3;
• windows in accordance with ISO 17651-1:2024, 5.4;
• acoustics in accordance with ISO 17651-1:2024, 5.5;
• heating, ventilation, and air conditioning systems in accordance with ISO 17651-1:2024, 5.6;
• cable ducts in accordance with ISO 17651-1:2024, 5.7;
• language displays in accordance with ISO 17651-1:2024, 5.8;
• electromagnetic radiation levels in accordance with ISO 17651-1:2024, 5.9;
• interior in accordance with ISO 17651-1:2024, 6.1 and 6.2.

The size of the signed language interpreting booth (Figure 5) is determined by the space required for the equipment and the need to provide the interpreting team with sufficient space to collaborate, while allowing them to enter and exit the booth without interfering with the camera image or disturbing one another. The booth shall be high and deep enough to provide the required volume of air, enabling adequate temperature control and draught-free air renewal.

The following minimum internal dimensions shall apply:

• width: 5,00 m;
• depth: 4,00 m;
• height: 2,30 m.

Figure 5 — Signed language interpreting booth floor plan

Figure 6 — Signed language interpreting booth (3D view)

Figure 7 — Signed language interpreting booth (back view)

Figure 8 — Signed language interpreting booth (A- cross sectional view)

Figure 9 — Signed language interpreting booth (B- cross sectional view)

The interpreter is positioned in such a way that allows them to have a view of the room and the rostrum (Figure 7). The interpreter is positioned at least 1 metre in front of the backdrop, facing the camera. The second interpreter is positioned at least 1 metre in front of the interpreter, facing the active interpreter.

The operation of the interpreting equipment, such as the camera, lights and video displays, can cause excessive temperatures in the signed language interpreting booth. The air conditioning in these booths shall have sufficient cooling power to maintain a temperature equal to that of the spoken language interpreter booths and shall allow for manual adjustment by the interpreters in the signed language interpreting booths.

General

The workspace shall have:

• lighting in accordance with 5.1 and 7.4.2.2;
• a backdrop in accordance with 5.2 and 7.4.2.3;
• visual display(s) in accordance with 5.3 and 7.4.2.4;
• a camera in accordance with 5.4 and 7.4.2.5;
• incoming sound in accordance with 5.5 and 7.4.2.9.

Lighting

The booth shall have lighting in accordance with 5.1 and with ISO 17651-1:2024, 6.3.

In accordance with ISO 17651-1:2024, 6.10, a three-point lighting system (one front, one indirect and one backdrop lighting source) shall illuminate the interpreter. The lighting sources shall be positioned in such a way as to avoid casting shadows on the hands or face of the interpreter or on the backdrop. They shall be dimmable, and lamps shall be used that produce low heat.

The side windows shall have adjustable blinds that can block the light from the dedicated booth to the adjacent booths.

NOTE Indoor windows with light coming in from the room are acceptable. However, natural incoming light from outside windows is not, since it may distort the required lighting settings for interpreting in the booth.

Backdrop

The backdrop shall meet the specifications in accordance with 5.2.

Display screen and video displays

The displays shall be provided in accordance with 5.3.

Two or more display screens with video displays (see ISO 11064-5^[20]) provide the incoming images and shall be in the direct line of sight of the signed language interpreter. These video displays shall be placed at a maximum distance of 2 metres from the interpreter. The video displays shall show:

1. Display screen 1 (main video display): the composite image as projected live to the audience, including the speaker or signer, the interpreter, slides, captions, and other content projected live.
2. Display screen 2: subtitles or live captions displayed in high contrast format (yellow letters on a black background).
3. Display screen 3: in case images or slides are not visible on the first video display, they shall be displayed on a third video display.

The main display screen shall have a diagonal of at least 40 inches. The other display screens shall be at least 24 inches. For information on a visual display to be visible, sufficient contrast with the background colour is necessary. The video display background therefore needs to be of a certain, different luminance and colour than the information displayed in accordance with ISO 9241-303.

NOTE Guidance on how to display captions or subtitles is provided in ITU-T T.701.25 ^[21].

Camera and pre-sets

The camera shall be provided in accordance with 5.4.

Image quality

The quality of the image shall conform to ISO 20109:2025, 5.2.1.

Control pedal

A control pedal shall be connected to the camera, as well as to the incoming sound device, to allow the interpreter to independently turn the camera on or off and to adjust the volume of the incoming sound (7.4.2.9) (see ISO 9241-400^[22]). The pedal shall be designed in conformity with the ergonomic accessibility principles in ISO 9241-20.

Anti-fatigue mat

To prevent strain, tiredness and possible injury, an anti-fatigue mat shall be provided for the interpreter to stand on.

Incoming sound

Incoming sound shall be provided through a wireless receiver in accordance with 5.5, connected to each interpreter's headphones, or with a loudspeaker.

NOTE Good results have been achieved with Radio Frequency (RF) receivers. Infrared (IR) receivers are not suitable as the interpreters' signing movements disrupt the infrared signal.

Each interpreter shall have their own individual receiver. The receiver and loudspeaker shall allow the interpreters to select either the floor or any of the interpreted languages and shall have a manual control to adjust the volume.

The interpreters' headphones shall conform to ISO 20109:2025, 8.3.1.

Electricity outlets shall be provided in accordance with ISO 17651-1:2024, 6.5.

Internet access shall be provided in accordance with ISO 17651-1:2024, 6.6.

A signed language interpreter's workspace in a hub shall be designed according to the requirements outlined for a dedicated signed language interpreting booth (see Clause 7) and in accordance with ISO/FDIS 17651-3.

If simultaneous delivery platforms are used, they shall conform to ISO 24019, and the use of audio, video, microphones, and headphones shall conform to ISO 20109.

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. The interpreter views the speakers or signers contributing from a separate location on a video display in accordance with 5.3. Where the interpreter is also separate to the audience, the interpreter views the audience on a video display in accordance with 5.3. Latency is less critical because the text and image signals of the speaker can be synchronised before reaching the interpreter. The applicable requirements for distance interpreting shall be in accordance with ISO 20109:2025, Clause 7.

Toilets shall be within easy reach of the workspaces for interpreters and preferably separate from the toilets used by attendees.

There should be an interpreters’ room within easy reach of the dedicated workspaces for interpreters for the exclusive use of interpreters and technical support staff when they are not on duty (see ISO 17651-1:2024^[23], 7.2).

A water fountain should be available nearby.

1. 
   (informative)
   
   Simplified checklists

Communicative event onsite without broadcast:

Demarcate interpreter workspaces on the floor of the hall (see 6.2.2, 6.3.4 and 6.3.5)

• Ensure a clear line of sight (see 4.2).
• No placement in front of a window or an area that produces a bright backlight (see 4.1).

Provide the technical equipment (see Clause 5, 6.2.3 and 6.3.6)

• Test the incoming sound (see 5.5). When working with spoken and signed language interpreters, test the incoming sound from the hall and the spoken language interpreting booths.
• Check with the interpreters the readability and the layout of the visual display with the interpreters (see 5.3).

Reserve seating for signing participants (see Annex C).

Communicative event on-site with broadcast:

Demarcate interpreter workspaces on the floor of the hall (see 6.3.4 and 6.3.5)

• Ensure a clear line of sight (see 4.2).
• No placement in front of a window or an area that produces a bright backlight (see 4.1).

Provide the technical equipment (see Clause 5 , 6.2.3 and 6.3.6)

• Pre-set the camera to the interpreters’ heights (see 5.4).
• Check the broadcast image of the interpreter on either the screen in the room or publicly, or both (see 5.4, 6.3.1 and Annex F).
• Test the incoming sound (see 5.5). When working with spoken and signed language interpreters, test the incoming sound from the hall and the spoken language interpreting booths.
• Check with the interpreters the readability and the layout of the visual display with the interpreters (see 5.3).

Reserve seating for signing participants (see Annex D).

1. 
   (informative)
   
   Flowchart

Figure B.1 — Flowchart of the working environment of signed language interpreters

1. 
   (informative)
   
   Workspace placements in meeting halls

Figure C.1 — Dedicated workspaces for interpreters with U-shaped seating

Figure C.2 — Dedicated workspaces for interpreters with oval shaped seating

1. 
   (informative)
   
   Workspace placements in conference halls

Figure D.1 — Dedicated workspaces for interpreters on the floor of a conference hall (in two signed languages), with a panel of signers and speakers at the rostrum

Figure D.2 — Dedicated workspaces for interpreters on the floor in a lecture hall

Figure D.3 — Dedicated workspaces for interpreters on the floor in a hemicyle

Figure D.4 — Dedicated workspaces for interpreters on the floor in a hemicycle, with a signer at the rostrum

1. 
   (informative)
   
   Layout of visual displays

Figure E.1 — Workspace with a single video display

Figure E.2 — One video display in the direct line-of-sight of the interpreter providing the incoming images as seen by the audience on the main screen

Figure E.3 — Workspace with dual video displays

1. 
   (informative)
   
   Broadcast image

When the communicative event is streamed with signed language interpretation, the following layout of the screen should be provided:

The composite image includes the speaker or signer and the interpreter, as well as captions, slides, and other projected content.^[1]1) The image of the interpreter can be displayed in:

1. Overlay mode one signed language (Figure F.1).
2. Picture in Picture one signed language (Figure F.2).
3. Picture in Picture two signed languages, option A (Figure 3 a).
4. Picture in Picture two signed languages, option B (Figure 3 b).

When a participant is making an intervention in a signed or spoken language, they should be shown in the main broadcast image.

The interpreter may be positioned on the left or the right side of the screen. The preferred placement should be based on local conventions and signing participants' specific needs.

Figure F.1 — Overlay mode

Figure F.2 — Picture in picture

The background behind the interpreter shall have a uniform colour, so that the image of the interpreter can be viewed without any visual distraction. The background colour value shall be mid-range. Recommended colours for the backdrop are grey or chroma blue.

Figure F.3 — Layout when there are two different signed languages

Bibliography

[1] ISO 23155, Interpreting services — Conference interpreting — Requirements and recommendations

[2] ISO 13611, Interpreting services — Community interpreting — Requirements and recommendations

[3] ISO 21998, Interpreting services — Healthcare interpreting — Requirements and recommendations

[4] ISO 20228, Interpreting services — Legal interpreting — Requirements

[5] ISO 17651-1, Simultaneous interpreting — Interpreters’ working environment — Part 1: Requirements and recommendations for permanent booths

[6] ISO 17651-2, Simultaneous interpreting — Interpreters’ working environment — Part 2: Requirements and recommendations for mobile booths

[7] ISO/FDIS 17651-3, Simultaneous interpreting — Interpreters’ working environment — Part 3: Requirements and recommendations for interpreting hubs

[8] ISO 20109, Simultaneous interpreting — Equipment — Requirements

[9] ISO 24019, Simultaneous interpreting delivery platforms — Requirements and recommendations

[10] ISO 22259, Conference systems — Equipment — Requirements

[11] ISO 20539:2023, Translation, interpreting and related technology — Vocabulary

[12] ISO 9241-112:2025, Ergonomics of human-system interaction — Part 112: Principles for the presentation of information

[13] AS/NZS 2107, Acoustics - Recommended design sound levels and reverberation times for building interiors

[14] ISO 6385, Ergonomics principles in the design of work systems

[15] ISO 9241-303:2011, Ergonomics of human-system interaction — Part 303: Requirements for electronic visual displays

[16] ISO 9241-303, Ergonomics of human-system interaction — Part 303: Requirements for electronic visual displays

[17] ITU-T Series H Supplement 1 (05/99) Application profile – Sign language and lip-reading real-time conversation using low bit-rate video communication

[18] S. Mishra, S. Gupta, R. Pahwa, M. H. Pinson, A. C. Bovik, "LIVE-ASL: Subjective and Objective Quality Assessment of American Sign Language Videos", University of Texas, USA; available at: https://live.ece.utexas.edu/research/LIVE-ASL-VQA/index.html [last accessed 17 October 2025]

[19] ISO 22259:2019, Conference systems — Equipment — Requirements

[20] ISO 11064-5, Ergonomic design of control centres — Part 5: Displays and controls

[21] ITU-T T.701.25 Guidance on the audio presentation of text in videos, including captions, subtitles and other on-screen text

[22] ISO 9241-400, Ergonomics of human—system interaction — Part 400: Principles and requirements for physical input devices

[23] ISO 17651-1:2024, Simultaneous interpreting — Interpreters’ working environment — Part 1: Requirements and recommendations for permanent booths

1. 1) ISO/IEC CD 20071-24, currently under development, will detail requirements for the visual presentation of signed languages. ↑