In 1902, Canadian-born Reginald A. Fessenden, together with two Pittsburgh millionaires, Hay Walker Jr. and Thomas H. Given, founded the National Electric Signaling Company (NESCO) in order to promote the inventor's efforts. NESCO made the bold decision to try to directly compete with Marconi, by setting up a transatlantic radiotelegraph service, operating between Brant Rock, Massachusetts and Machrihanish, Scotland. Although Fessenden did achieve some initial success, including the first two-way trans-Atlantic communication by radio, the effort abruptly ended in December 1906, when the Machrihanish antenna collapsed.

In February 1909, NESCO won an important Navy contract, to supply a Fessenden-designed 100-kilowatt rotary-spark transmitter for a new high-power station being constructed in Arlington, Virginia. However, NESCO's transmitter failed to fully meet the contract specifications, and even worse, in 1913 the Navy determined that Federal Telegraph arc-transmitters were clearly superior, so Federal Telegraph ended up getting the transmitter contracts. Meanwhile, Fessenden's relations with NESCO's financial backers were becoming increasingly estranged, until finally, on December 28, 1910, the company's management attempted to seize the Brant Rock office records, while simultaneously enjoining Fessenden from further participation in company activities. Fessenden, who was formally dismissed from the NESCO the following month, sued the company for breach of contract, and the ensuing legal entanglements forced NESCO into receivership. At this point Fessenden permanently left the radio field, while a crippled NESCO struggled on as a minor company through World War One. In 1919 NESCO was taken over by Westinghouse and became part of RCA.

There is also the National Electric Supply Co., which is obviously the same establishment.