from 1928 onward, syndicated radio programming was distributed on 78 rpm discs. the desirability of longer continuous playing time soon led to the adoption of the vitaphone soundtrack disc format. beginning in about 1930, 16-inch  rpm discs playing about 15 minutes per side were used for most of these "electrical transcriptions". some transcriptions were, like soundtrack discs, pressed with the commencement at the center of the disc and the needle moving outward (in the era of shellac pressings and steel needles, needle wear considerations dictated an 'inside start' for such a long recording); conversely, some commenced at the edge.