7. A system comprising: one or more computers and one or more storage devices storing instructions that are operable, when executed by the one or more computers, to cause the one or more computers to perform operations comprising: displaying a graphical user interface for language translation on a user device that includes (i) one or more automated speech recognizers that recognize speech in a source language only when in a first mode and to recognize speech in a target language only when in a second mode, (ii) a microphone that receives audio, and (iii) a speaker that outputs audio, the graphical user interface comprising a source language visual indicator and a target language visual indicator; in the first mode in which the one or more automated speech recognizers recognize speech in the source language only, highlighting the source language visual indicator and displaying an input visual indicator on the graphical user interface to provide a visual indication that the user device receives audio input in the source language only; and in response to an endpointer on the user device automatically determining that the input in the source language only has completed, and without requiring the user to manually switch between the first mode and the second mode, automatically activating the second mode in which the one or more automated speech recognizers recognize speech in the target language only, removing highlighting from the source language visual indicator, highlighting the target language visual indicator, and replacing the input visual indicator with an output visual indicator on the graphical user interface to provide a visual indication that the user device provides audio output in the target language.
10. The system of claim 7 , wherein the visual indication that the user device provides audio output in the target language is provided by highlighting the output visual indicator on the graphical user interface while highlighting the target language visual indicator.