distribution board vs switchboard

distribution board

noun
  • A board containing multiple electrical fuses or circuit breakers; a panelboard 

switchboard

noun
  • A large piece of power-distribution equipment that directs electricity to multiple loads. 

  • The electronic panel that is used to direct telephone calls to the desired recipient. 

How often have the words distribution board and switchboard occurred in a corpus of books? (source: Google Ngram Viewer )