Original electrical trade vintage catalog for OPERADIO MANUFACTURING COMPANY, was located in St. Charles, IL. Manufacturers of Sound Equipment, Intercom. Sound Amplifying Equipment, Radio Speakers, Paging Systems, Radio Program Pre-selectors, Automatic Watering Systems, Nowire Servant Calls and Intercommunicating Systems. Disbound from a large 1938 electrical construction materials book, this unique old one page technical specifications brochure would display wonderfully matted and framed. A marvelous addition to your retro electric equipment library.