Mr. Warner first launched the Warner Instrument Company in 1904 to manufacture cut meters that were used to measure the speed of industrial machinery. Warner's next major venture revolved around his invention of the automobile speedometer, based on the same magnetic principle used in the cut meter. The first speedometers were sold as add-on devices. Mr. Warner never dreamed that the speedometer would be such an astounding success. In fact, he once declared; "We did not think the auto-meter had any future. It was only a luxury gadget which we used to promote the cut meter."
After selling the patent rights for the speedometer to the Stewart Electric Company, Mr. Warner turned to other new products, including the manufacture of two wheel trailers and the first ever tourist trailer, predecessor of today's pop-up campers. In 1927, he organized still another company - the Warner Electric Brake Corporation, based on a new design of brake using electricity.