Some patent links of Norman C. Pickering related to phonograph reproduction

https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=US&NR=2538164A&KC=A&FT=D&ND=3&date=19510116&DB=EPODOC&locale=en_EP



https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=US&NR=2543127A&KC=A&FT=D&ND=3&date=19510227&DB=EPODOC&locale=en_EP