Control system for printing machine

A single pass multi-colour electrophotographic printing machine, comprises a photoconductive member (10) defining a timing aperture, the member moving along a path in a printing machine and a plurality of imaging devices (C,D), each one of the plurality of imaging devices writing a latent image on the photoconductive member (10). The system further includes a sensor (100), located adjacent the photoconductive member (10), to sense the aperture in the photoconductive member (10) as it passes the sensor (100) and generate a signal indicative thereof and a control device (90), which generates a timing signal for each of the plurality of imaging devices (C, D) as a function of the signal generated by the sensor (100) and a plurality of predetermined parameters.