 By about 1936, 16-inch aluminum-based discs coated with cellulose nitrate lacquer, commonly known as acetates and recorded at a speed of 33 rpm, had been adopted by the networks and individual radio stations as the standard medium for recording broadcasts.The making of such recordings, at least for some purposes, then became routine.Some discs were recorded using a "hill and dale" vertically modulated groove, rather than the "lateral" side-to-side modulation found on the records being made for home use at that time.