Wheeler sound powered phone

The Wheeler sound-powered telephone was made by The Wheeler Insulated Wire Company, Inc. (later a division of The Sperry Corporation), located in Waterbury, Connecticut. These rugged, battery-free communication devices—such as the widely recognized Wheeler SPT-102 emergency set—were primarily manufactured and deployed during the 1940s and 1950s. They were extensively used during World War II and the post-war era for military, maritime, and industrial emergency backup communications because they operate entirely on the kinetic energy of the user's voice rather than an external power source.