Section 73.402 - Definitions(a)DAB. Digital audio broadcast stations are those radio stations licensed by the Commission and use the In-band On-channel ("IBOC") system for broadcasting purposes.(b)In Band On Channel DAB System. A technical system in which a station's digital signal is broadcast in the same spectrum and on the same channel as its analog signal.(c)Hybrid DAB System. A system which transmits both the digital and analog signals within the spectral emission mask of a single AM or FM channel.(d)Extended hybrid operation. An enhanced mode of FM IBOC DAB operation which includes additional DAB subcarriers transmitted between the analog FM signal and the inner edges of the primary DAB sidebands.(e)Primary AM DAB Sidebands. The two groups of hybrid AM IBOC DAB subcarriers which are transmitted 10 to 15 kHz above carrier frequency (the upper primary DAB sideband), and 10 to 15 kHz below carrier frequency (the lower primary DAB sideband).(f)Multicasting. Subdividing the digital bitstream into multiple channels for additional audio programming uses.(g)Datacasting. Subdividing the digital bitstream into multiple channels for additional data or information services uses.(h)All-digital AM station. An AM station broadcasting an IBOC waveform that consists solely of digitally modulated subcarriers and the unmodulated AM carrier.(i)Asymmetric sideband operation. For digital FM stations, the use of different power levels on the upper and lower digital sidebands in a hybrid or extended hybrid DAB system. 72 FR 45692 , Aug. 15, 2007, as amended at 85 FR 78027 , Dec. 3, 2020 85 FR 78027 , 1/4/2021; 89 FR 84103 , 11/20/2024