[269 U.S. 459, 460] Mr. Wm. H. Davis, of New York City, for petitioner.

Mr. John W. Davis, of New York City, for respondent.

Mr. Chief Justice TAFT delivered the opinion of the Court.

The Radio Corporation, a corporation of Delaware, filed a bill in equity in the Southern district of New York, joining with itself the De Forest Radio Telephone & Telegraph Company, also of Delaware, as coplaintiff, against the Independent Wireless Telegraph Company of Delaware and the American Telephone & Telegraph Company of New York. The case made in the bill was this: [269 U.S. 459, 461] Lee De Forest invented and received patents Nos. 841,387 and 879,532, dated in 1908 and 1909, for devices for amplifying feeble electric currents and certain new and useful improvements in space telegraphy. After giving limited licenses of the American Telephone & Telegraph Company, he assigned the patents to the De Forest Radio Telephone & Telegraph Company. On March 16, 1917, the De Forest Company, by writing duly recorded, gave an exclusive li