patchboard vs switchboard

patchboard

noun
  • A component of a manual telephone switchboard, or of various early data processing equipment, in which circuits are completed with cords on a matrix of connections. 

switchboard

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

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

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