This was years prior to the joint patent of electric telegraphy by William Fothergill Cooke and Charles Wheatstone taken out in 1837 in England.
More Silicon Valley companies have offices overseas, the study says, and there has been a sharp rise in the joint patents with foreign companies.
Their joint patent described two versions of a design with no poles: the "closed-core transformer" and the "shell-core transformer".
A total of 110 are known to have been built by 1733 when the joint patent expired, of which 14 were abroad.
Ezra T. Gilliland, of Boston, had become associated with him in his experiments, and they took out several joint patents subsequently.
Roper and Christopher Miner Spencer were granted a joint patent for a repeating shotgun mechanism on 4 April, 1882.
Thomas was persuaded to secure a joint patent in survivorship with his son.
Successful, he returned to England and invented a telephone crosstalk reduction circuit, which was adopted internationally from 1927 under his joint patent with J. P. Johns.
In 1545 Hales and Sadler were granted a joint patent for the office.
Pepper saw the concept and replicated it on a larger scale, taking out a joint patent with Dircks.