Poulsen Arc Transmitter working model, 1909

This one-of-a-kind "working model" or prototype of a 25 watt Poulsen Arc Transmitter was built by Douglas Perham and Cyril Elwell at the Poulsen Wireless Telegraph and Telephone Company laboratory in Palo Alto, California, probably in late 1909. Earlier, while in Denmark, Elwell had purchased the right to manufacture Poulsen arcs in the United States, and immediately began to improve on the design. This prototype remained on display at the Palo Alto offices of Poulsen Wireless's successor, Federal Telegraph Company, until the company moved east in 1932. It was rescued by former chief engineer Leonard Fuller, who later returned it to Cyril Elwell. Elwell presented the model to Douglas Perham.