Short answer: one booth per outgoing language, at least two interpreters in each booth, and one channel per language plus one for the floor sound. For a conference running in Turkish and English that means one booth, two interpreters, two channels and one receiver for every guest who will listen to interpretation. Size the receiver count on the guests who actually need translation rather than the full headcount, then add spares. The reference standard for booths has changed too: EN ISO 17651-2 was published on 19 February 2024 and EN ISO 4043:2016 was withdrawn in its favour.
How many booths and how many interpreters?
The booth count is the easy part: one booth per outgoing language. The AIIC checklist for simultaneous interpretation equipment states it plainly, and adds that two-way booths, working into two languages, need three consoles and the right outgoing channels. Interpreter numbers depend on how long the programme runs. Under the working conditions published by TKTD, the Turkish Conference Interpreters Association, a minimum of two interpreters forms a team and a single interpreter may not work beyond 45 minutes, and only in exceptional cases. The same text caps a two-interpreter team at 2 x 3 hours per day, requires a lunch break of at least an hour, and calls for a third interpreter or a second team once a meeting passes six hours. The reason is cognitive load rather than cost: AIIC notes that interpreters work in stints of 20 to 30 minutes to hold quality. So a dealer meeting that starts at 09:00 and ends at 17:00 cannot be staffed with two interpreters.
How many channels, and when does relay start?
Channel count follows language count: one outgoing channel per language, plus one channel carrying the floor sound. A conference in Turkish, English and Arabic has three booths, three outgoing channels and one floor channel, so four in total. The hardware ceiling sits well above that. Bosch states its INTEGRUS infrared language distribution system provides a maximum of 32 audio channels, the floor plus up to 31 languages, and that pocket receivers come in 4, 8 or 32 channel versions. Declare your language count while you are still specifying the rental, because a four channel receiver will not show a fifth language. Beyond two languages, relay enters the conversation. Relay means a language is interpreted through an intermediate language instead of directly. The European Parliament works in 24 official languages, which produces 552 language combinations, and it runs relay through English, French and German. TKTD asks that booth and interpreter numbers be arranged to avoid systematic relay. Every language left dependent on a relay chain carries a small delay and a real risk of losing nuance.
The booth standard changed: ISO 17651 replaced ISO 4043
Mobile booths were specified against ISO 4043 for decades. That ended in 2024. EN ISO 17651-2:2024 was published on 19 February 2024 and EN ISO 4043:2016 was withdrawn, while permanent booths moved under ISO 17651-1:2024. The European Commission's list of standards for interpreting facilities now names ISO 17651-1:2024 for permanent booths, ISO 17651-2:2024 for mobile booths, ISO 17651-3:2026 for interpreting hubs, ISO 24019:2022 for interpreting delivery platforms, ISO 20109:2025 for equipment and ISO 22259:2019 for conference systems. The equipment standard reached its second edition in May 2025. In Turkey, TSE published earlier members of the family as TS EN ISO 2603, TS EN ISO 4043 and TS EN ISO 20109, and TKTD requires equipment to meet the current ISO or TSE standards. Two questions are worth putting to a supplier: which edition was the booth built to, and how many times has it been assembled? ISO 4043 required a mobile booth to hold its initial sound insulation performance for at least 100 uses. A frame that has travelled for years with loose panels passes on paper and leaks sound in the room.
Where do booths go? 30 metres and 30 degrees
Dimensions and siting shape what interpreters can actually do. Per the AIIC checklist, a mobile booth seating two or three interpreters in comfort measures 1.60 to 2.40 m wide, 2 m high and 1.60 m deep, with a working surface running the full width of the booth and at least 45 cm deep. The front needs a single window 80 cm high in non-reflecting glass, and the entrance needs a door that opens outwards rather than a curtain. Distance is the figure that decides everything: booth to rostrum should not exceed 30 m, with 20 to 25 m preferred. If the room forces a longer run, put a monitor in the booth and a camera on the rostrum. The minimum sideways angle for reading a screen is 30 to 35 degrees, which is why booths along a side wall are angled in a fish-bone formation. Raising them onto a platform of 25 to 30 cm lets interpreters see the room over the delegates' heads. TKTD likewise requires booths to sit where the speaker, the rostrum and the projected material are easy to see. Leave at least 2 m between the delegate tables and the booths, and keep a 1.5 m passage behind them for fire safety.
Infrared or radio frequency?
Interpretation reaches the audience over one of two paths: infrared light or radio. Infrared does not pass through walls and ceilings, and Bosch presents that limitation as a confidentiality feature, since the signal never leaves the room. The technical frame is IEC 61603-7:2003, which defines multi-channel infrared audio transmission for conference interpretation in the 45 kHz to 1 MHz and 2 MHz to 6 MHz bands. Those bands sit above lighting systems, so light does not create interference, and the manufacturer quotes a signal to noise ratio above 80 dB. The trade-off is line of sight. If the radiator panels cannot see the guest, the audio drops out: columns, low-hanging chandeliers, strong sunlight through a glass roof, and guests who put the receiver in a jacket pocket are the usual culprits. The fix is more radiators at better angles, not more volume. Radio systems, tour guide sets in particular, win with groups on the move: factory visits, site tours, dealer walk-arounds. Because they pass through walls, they are not the first choice for closed sessions where confidentiality matters.
Receiver counts, charging and the handout desk
Base the receiver count on the guests who will listen to interpretation, then add 5 to 10 percent as spares. Charging is the item most plans forget. Manufacturer figures for INTEGRUS receivers give battery life of up to 200 hours on alkaline cells and up to 75 hours on a battery pack, with charging units taking up to 56 receivers and a full charge in 105 minutes. Across a two day congress those numbers set how many receivers you can have ready by morning, so on a 400 guest programme charger capacity belongs on the rental list. Set the handout desk at the entrance, release units against an ID or a business card, and print the channel map on the desk and on the booth's language panel: channel 1 Turkish, channel 2 English. Guests wandering out with a receiver during the coffee break is the main source of loss, and one steward at the door usually saves the count. For hygiene, disposable ear pads or replaceable foam covers do the job.
Take the sound and the technician seriously
The first variable in interpretation quality is not the interpreter, it is the audio arriving in the interpreter's headphones. The AIIC checklist calls for equipment that supplies the full range of sound from 125 to 12,500 Hz, dedicated conference microphones, and every microphone monitored from the central console where the technician sits. The same document advises against combining a hotel's own public address microphones with the interpretation system, and names faulty hotel microphones as the most frequent cause of disruption in hotel meetings. A qualified technician should stay in the room throughout, seated with a clear view of the console, the booths and the screen. Fit a lapel or headset microphone to any speaker who leaves the rostrum, because a presenter walking a handheld microphone in front of a loudspeaker puts ring into the room and into the interpretation channel. For remote and hybrid setups the framework is ISO 24019:2022 together with ISO 20108, which cover the quality of sound and image reaching interpreters, latency and lip sync. A remote interpreter seeing the speaker and the slides is not a preference, it is a working condition.
What to have ready before you ask for a quote
Istanbul's international meeting volume puts this topic on the table for a lot of corporate programmes. According to ICCA's GlobeWatch 2025 report, the city hosted 95 large scale international congresses in 2025, ranking 13th in Europe and 18th worldwide, while Turkey held 33rd place globally with 142 congresses. Before you ask for a quote, gather this: which languages will run and which one is the floor, how many hours and how many sessions, how many guests will listen to interpretation, the room plan and where booths can stand with a view of the rostrum, whether there will be a stream or a recording, and whether presentation files can go to the interpreters in advance. That last item is the cheapest quality gain available: an interpreter who receives the glossary and the slides a day early is measurably clearer in the room. Tales Event delivers interpretation systems, booths, sound, lighting, staging and LED across Turkey with a single crew, so when the interpretation plan is drawn on the same table as the stage design, sightlines from the booth and the receiver desk both end up inside the run of show.
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