Image forming equipment having an image carrier and a developer carrier located face-to-face and forming an AC-superposed DC electric field between them to develop a latent image electrostatically formed on the image carrier. Sensors responsive to image forming conditions are provided and protected from...http://www.google.com.au/patents/US5270783?utm_source=gb-gplus-sharePatent US5270783 - Image forming equipment having improved toner sensing
