One of the better known experimenters with mechanical television was
Charles Francis Jenkins, a prolific American inventor. In May 1920,
at the Toronto meeting of the Society of Motion Picture Engineers,
Jenkins introduced his prismatic rings as a device to replace the
shutter on a film projector. This invention laid the foundation for
his first "radiovision" broadcast. He claimed to have transmitted the
earliest moving silhouette images on June 14, 1923, but his first
public demonstration of these did not take place until June of 1925.
Jenkins Laboratories constructed a "radiovision transmitter", W3XK, in
Washington D.C. The short-wave station began transmitting "radiomovies"
across the Eastern U.S. on a regular basis by July 2, 1928. Jenkins
wrote in 1929:
"This gave the amateur action-pictures to 'fish' for; and during
August following a hundred or more had finished their receivers and
were dependably getting our broadcast pictures, and reporting
thereon, to our great help."