There is no need to replace worn-out developer, as the user effectively replaces it along with the toner. An alternative developing system, developed by KIP from an abandoned line of research by Xerox, completely replaces magnetic toner manipulation and the cleaning system, with a series of computer-controlled, varying biases. The toner is printed directly onto the drum, by direct contact with a rubber developing roller which, by reversing the bias, removes all the unwanted toner and returns it to the developer unit for reuse.