Abstract: A bi-directional data communications system and associated methods of high speed data communication for transferring data over a three phase power system are provided. Transmission of information uphole is performed using either sequential or simultaneous multiple frequency transmissions, selected to avoid known sources of electric noise. The frequencies are transmitted such that a combination of multiple frequencies or a pattern of frequency transmissions represents the transmitted data. Frequencies used for uphole transmission can be adaptively adjusted by downhole communication of data interpreted by the downhole unit. Digital signal processing including time and frequency domain techniques are used to decode the transmitted data.