Recommendation ITU-T G.9902 contains the physical layer (PHY) and the data link layer (DLL) specifications for the ITU-T G.9902 narrowband orthogonal frequency division multiplexing (OFDM) power line communication transceivers operating over alternating current and direct current electric power lines over frequencies below 500 kHz. This Recommendation supports indoor and outdoor communications over low voltage-lines, medium-voltage lines, through transformer low-voltage to medium-voltage and through transformer medium-voltage to low- voltage power lines in both urban and long-distance rural communications. This Recommendation addresses grid to utility meter applications, advanced metering infrastructure (AMI) and other 'Smart Grid' applications such as the charging of electric vehicles, home automation and home area network (HAN) communications scenarios. This Recommendation does not contain the control parameters that determine spectral content, power spectral density (PSD) mask requirements and the set of tools to support a reduction of the transmit PSD; all of which are detailed in [ITU-T G.9901].