An improved method and apparatus for monitoring the amount of use sustained by a replaceable part within an electrophotographic printing apparatus is disclosed. In response to a print command, a controller reads data from a permanent memory within the replaceable part. The data, which indicates how much...http://www.google.ca/patents/US5489971?utm_source=gb-gplus-sharePatent US5489971 - Method and apparatus for detecting an exchange period for parts within an electrophotographic printing apparatus
