This machine does not use developer, so a TD sensor is not necessary. In each AIO unit, the toner supply roller [A] supplies toner to the development roller [B]. Electrostatic attraction generated by the friction between the toner supply roller and development roller moves toner to the surface of the development roller, and the development blade [C] makes sure that the layer of toner on the development roller has an even thickness.
The discharge sheet [D] removes development roller bias.