The U. S. Navy discovered a new use for the Telegraphone in World War I. In 1914 Germany used wire recorders purchased from the American Telegraphone Company to transmit high-speed wireless telegraph messages to German submarines in the Atlantic. Only another Telegraphone operating at high speed could record the messages and make them intelligible at a slower speed. Charles Apgar, an employee of the American Marconi Company, was operating an amateur radio station W2MN and had developed an amplifier using a DeForest Audion tube. He picked up the German radio transmissions, amplified them through a loudspeaker and recorded them on Dictaphone cylinders and gave them to the government. Secretary of the Navy Josephus Daniels ordered the Navy to seize the German radio station in Sayville NY on July 8, 1915, to stop the use of its Telegraphones by German spies. The Naval Research Laboratory in Washington began research on magnetic recording with 4 Telegraphones purchased from the American Telegraphone Company. In 1921 W. L. Carlson and Glenn L. Carpenter filed for patent 1,640,881 on the application of ac bias to the record head to improve the quality of telegraph signals. But as Poulsen had discovered, magnetic recording was not yet practical and ac bias would be forgotten when the Navy ended its experiments.