episode vs phone-in

episode

noun
  • An instalment of a drama told in parts, as in a TV series. 

  • An incident, action, or time period standing out by itself, but more or less connected with a complete series of events. 

phone-in

noun
  • A show requiring members of the public to telephone the studio. 

How often have the words episode and phone-in occurred in a corpus of books? (source: Google Ngram Viewer )