Demonstration Wireless Telegraphy Coherer Receiver

Demonstration Wireless Telegraphy Coherer Receiver, early 20th century, by The United States Electrical Supply Co. , New York , with Bunnell sounder, twin supports for coherer, tightening screw and electric bell for de-coherer, on mahogany base with binding posts and three metal feet, ht. 15 in. (lacking coherer and sounder adjusting spring). Following Marconi's invention of wireless telegraphy, a number of scientific and electrical manufacturers offered similar demonstration receivers, which would have only been powerful enough to transmit across a short distance, but were sufficient to show the workings of this latest marvel. A few companies also offered similar instruments as toys, although they were probably very much the same. Unlike patent infringers such as Lee De Forrest, Marconi did not seem too concerned and doesn't appear to have sued them.