Abstract: An electrostatographic single-pass multiple station multi-color printer for forming an image onto a web has a plurality of toner image-printing electrostatographic stations. Each station has a drum onto the surface of which a toner image can be formed. An exposure station forms an electrostatic toner image line-wise on each drum surface. A corona device transfers the toner image onto the web, which is conveyed in succession past the stations in synchronism with the rotation of the drum surface. Register control apparatus provided for controlling the operation of each of the stations in timed relationship thereby to obtain correct registering of the distinct toner images on the web. The register control apparatus comprises an encoder driven by the displacement of the web to produce pulses indicative of web displacement, and a delay arranged to initiate the operation of subsequent stations after a predetermined web displacement, as measured by the encoder, has occurred.