Simultaneous translation is done (almost) in real time as the source-language speaker delivers their message. It requires the requisite technical equipment (interpretation booth, sound equipment, receivers with headphones).
Because of the demanding and intense concentration, interpreters work in tandem, each approximately for 30 minutes before switching.
For smaller groups, or during factory tours, a tour guide system (also called whispering equipment) is used. The interpreter must be able to see and hear the speaker without interference.