Abstract: The present invention relates to a system for communicating between two integrated circuits (ICs) or within an IC. The ICs are either on the same circuit boards or on different circuit boards with a common backplane. The system comprises a first integrated circuit having an output circuit for generating phase shift keying signals and a second integrated circuit having an input circuit for decoding the phase shift keying signals. The output circuit may include a ring oscillator for generating multiple clock signals that are phase-locked to one another.