The invention is generally directed towards monitoring of a signal (m), such as a clock signal or a data signal, by sampling the signal to obtain a discrete sample representation of the signal and analyzing the sample representation. The idea according to the invention is to slide a sample window (sw) over the sampled signal and determine whether the samples currently within the window include a valid transition sequence. in the general case, the existence of a valid signal is confirmed as long as a valid transition sequence is present in at least one of a predetermined number of consecutive sample windows. in order to reduce the need for oversampling in high-frequency applications, the invention furthermore proposes a multi-phase sampling technique according to which a number of phase-shifted sample clocks (s1 to sn) are generated for the purpose of sampling the signal to be monitored. Higher-frequency oversampling is thus replaced by a higher resolution in the time domain.