Often times the rabbi will repeat the same passage in English so the deaf audience still gets the message in at least one language. Another interpreting option is to mouth the Hebrew words as best as possible. If the deaf person is familiar with the expression or prayer, this may be meaningful to them. In this case the interpreter may sign from the English. This is most useful to deaf people who are familiar with the Hebrew pronunciation or who are trying to learn the Hebrew words.
Some prayer books have the Hebrew written out phonetically already.
However, the phonetic spellings are not consistent from one book to the next. If the prayer book does not have a transliteration, the interpreter must be able to read Hebrew in order to spell out each word. This can be very time consuming and difficult to keep up with longer passages. The next three options are for interpreters who are able to translate from Hebrew into sign language. Other interpreters listen to the Hebrew, mouth the Hebrew, and sign the meaning of each Hebrew word.