“Edison was adamant that Edison recordings would be played only on Edison phonographs. His competitors, Victor and Columbia, shared the same playback technique, etching a laterally cut groove that sent the needle moving horizontally as the record played. Their recordings could be played on one another’s machines. Edison, however, adopted his own design, a groove that varied vertically, called at the time a “hill and dale” cut. An adapter permitted Victor records to be played on an Edison Disc Phonograph, but Edison forbade the sale of an attachment that permitted his records to be played on competitors’ machines.”
From “Edison the Inventor, Edison the Showman” – The New York Times.