answer: Before doing the experiment, #Person1# tells students to pay attention to safety and sign their names. #Person1# will change #Person2#'s air compressor.
documents: #Person1#: Good afternoon, everyone. The experiment is to start at 3. Have you gone through the instructions?
  #Person2#: Yes, sir.
  #Person1#: Ok, now some points for attention. First of all, pay attention to safety. . . Now, sign your names on the lab record, and after that you can start. If there is any question, just let me know.
  #Person2#: Excuse me, sir. This air compressor doesn't work.
  #Person1#: Have you turned it on?
  #Person2#: Yes, I have.
  #Person1#: Ok, I will get you another one.
  #Person2#: Thank you.