systems and method are described for clock recovery or detection of rapid phase transients . an apparatus includes : a numerically controlled oscillator ; a phase detector coupled to the numerically controlled oscillator ; and a multiplexer coupled to the phase detector and the numerically controlled oscillator , wherein a ) the phase detector sets a state variable indicator to either i ) a high value when an output phase of the numerically controlled oscillator lags an incoming signal phase , or ii ) a low value when the output phase leads the incoming signal phase , b ) the multiplexer sends either i ) a high increment to the numerically controlled oscillator when the state variable indicator has been set to the high value , or ii ) a low increment to the numerically controlled oscillator when the state variable indicator has been set to the low value , and c ) the numerically controlled oscillator either i ) advances the output phase when the high increment has been sent to the numerically controlled oscillator , or ii ) retards the output phase when the low increment has been sent to the numerically controlled oscillator .