capacitor 30 in fig.3 (http://patentimages.storage.googleapis.com/pages/US2959741-1.png)
(http://patentimages.storage.googleapis.com/pages/US2959741-1.png)
US-pat.#2959741 (http://worldwide.espacenet.com/publicationDetails/originalDocument?CC=US&NR=2959741A&KC=A&FT=D&ND=3&date=19601108&DB=EPODOC&locale=en_EP)