A signal transmitting device includes an output control circuit and a transmitting circuit. The output control circuit generates a first encoded symbol, a second encoded symbol, a third encoded symbol, and a fourth encoded symbol and an inverted flag signal by inverting the logic levels of second bits of a first symbol, a second symbol, a third symbol, and a fourth symbol, and generates a first output control signal and a second output control signal based on the first to fourth encoded symbols, when the maximum transition is present among the first to fourth symbols. The transmitting circuit may transmit the inverted flag signal and a Tx (Transmit) signal generated based on the first and second output control signals.