Simultaneous interpreters practically instantly transfer a speech or presentation from one language to another. It is often offered in multiple languages at international events. Due to the high levels of concentration required the simultaneous interpreters work in teams of at least two and take turns about every 30 minutes.
Simultaneous interpreting can either be offered with the help of an interpreting booth, or a “tour guide” system. However, booths clearly offer a superior quality for the listeners and are definitely the best solution for large events, while tour guide systems offer a good solution for mobile events. Whispered interpreting, so called "chuchotage" is a special form of simultaneous interpreting for a maximum of two listeners.