answering machine vs voicemail

answering machine

noun
  • A device that automatically records voice mail from unanswered telephone calls. 

voicemail

noun
  • A computerized interactive system for storing, processing and reproducing verbal messages left through a conventional telephone network. 

  • An individual message on such a system. 

How often have the words answering machine and voicemail occurred in a corpus of books? (source: Google Ngram Viewer )