A differential tension control mechanism is provided to balance the
tension difference across the web. The differential tension control can
alternatively be implemented on donor take-up and supply rollers. They
also prevent the lateral movement of the donor in the nip region. They
also improved the quality of print. They tended to generate a lot of
movement between the print units. The tension control differential also works in conjunction with phase shifting and speed-correcting right angle differentials. The tension control system comprises a microprocessor that combines with a dedicated signal processor to provide a simple and reliable method of adjusting and controlling web tension.