A method and an apparatus for controlling the toner concentration of a dry developer, including a magnetic carrier and a non-magnetic toner, used in a magnetic brush developing system. The system includes an inherent magnetic means and an inheret circulation path through a portion of which a steady stream...http://www.google.com.au/patents/US4200665?utm_source=gb-gplus-sharePatent US4200665 - Method for controlling the toner concentration of a developer used in a dry type developing system
