A method of regulating a target system generates a plurality of digital signals which define a reference pulse train with a frequency dependent upon a reference signal. A target system to be regulated (such as a transport speed of a paper transport assembly in a printer) has an output in the form of a plurality of digital signals defining a feedback pulse train having a frequency. The frequency of the reference pulse train is compared with the frequency of the feedback pulse train. A control signal is generated dependent upon the frequency comparison, and is provided as an input to the target system.