The first radiotelephony signals were sent and received in 1906, but these were experiments to show feasibility and not intended as entertainment. But in 1906, Lee DeForest invented the grid-modulated vacuum tube, which he designated the "audion". This enormously infuential device made radiotelephony practical and enabled the explosion in commercial and entertainment electronics that began after the conclusion of WWI. As an employee of Fedral Telegraph Company, DeForest had his laboratory in Palo Alto, CA for a period beginning in 1910, where he was able to revise the "audion" to reliably perform as an amplifier. The site of the DeForest laboratory is only a few blocks distant from the site of the Museum of American Heritage.