power supply vs switchboard

power supply

noun
  • A source of power such as the mains or a generator. 

  • That part of a piece of electronic apparatus that provides appropriate voltages for the rest of the electronics from the connected AC source. 

  • Used other than figuratively or idiomatically: see power, supply. 

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 power supply and switchboard occurred in a corpus of books? (source: Google Ngram Viewer )