Canadian-born Reginald Aubrey Fessenden (1866-1932), one of the principal early radio inventors and the first important inventor to experiment with wireless, left the University of Pittsburgh in 1900 to work for the U.S. Weather Bureau. There he invented the liquid barretter, an early radio receiver and attempted to work out a means for wireless transmission of weather forecasts. After a squabble over patent rights, Fessenden resigned in 1902.

The National Electric Signaling Company (NESCO), primarily intended to support Fessenden's work on wireless, telegraphy and telephony, was formed by Fessenden and two Pittsburgh capitalists, Hay Walker, Jr. and Thomas H. Given. It began as an inventor's laboratory and never proved successful as a business venture.

Fessenden recognized that a continuous wave transmission was required for speech and he continued the work of Nikola Tesla, John Stone Stone and Elihu Thomson on this subject. Fessenden felt he could also transmit and receive Morse code better by the continuous wave method than with a spark-apparatus as Marconi was using.

In 1903 Fessenden's first high-frequency alternator needed for continuous wave transmission was built to his specifications by Charles Steinmetz of GE. In 1906 Fessenden obtained a second alternator of greater power from GE and on Christmas Eve broadcast a program of speech and music. The work on this alternator was given to Ernst F. W. Alexanderson. It took years for Alexanderson to develop an alternator capable of transmitting regular voice transmissions over the Atlantic.

But by 1916 the Fessenden-Alexanderson alternator was more reliable for transatlantic communication than the spark apparatus.

Fessenden also worked on continuous-wave reception. This work arose out of his desire for a more effective type of receiver than the coherer, a delicate device that was limited by its sensitivity on a rolling ship at sea. In 1903 he developed a new receiving mechanism - the electrolytic detector.

As his work progressed Fessenden evolved the heterodyne system. However, due to faulty construction and the fact that it was ahead of its time, heterodyne reception was not fully appreciated until the oscillating triode was devised, thus allowing a practical means of generating the local frequency.

Between 1905 and 1913 Fessenden developed a completely self-sustaining wireless system. However, constant quarrels between Fessenden, Walker and Given culminated in Fessenden's forming The Fessenden Wireless Company of Canada. He felt a Canadian company could better compete with British Marconi. As a result, his backers dismissed Fessenden from NESCO in January of 1911. Fessenden brought suit, won and was awarded damages.

To conserve assets pending appeal, NESCO went into receivership in 1912, and Samuel Kintner was appointed general manager of the company.

In 1917 Given and Walker formed International Signal Company (ISC) and transferred NESCO's patent assets to the new company. Westinghouse obtained majority control of ISC through the purchase of $2,500,000 worth of stock. The company was then reincorporated as The International Radio Telegraph Company. The Westinghouse-RCA agreements were signed in 1921 and International's assets were transferred to RCA.