NO. 836 PIONEER ELECTRONICS RESEARCH LABORATORY – This is the original site of the laboratory and factory of Federal Telegraph Company, founded in 1909 by Cyril F. Elwell. Here, Dr. Lee de Forest, inventor of the three-element radio vacuum tube, devised the first vacuum tube amplifier and oscillator in 1911-13. Worldwide developments based on this research led to modern radio communication, television, and the electronics age. Location: In sidewalk, SE corner of Channing Ave and Emerson St, Palo Alto.