There is known a developing cartridge including a developing roller. The developing cartridge is detachably attachable to an image-forming apparatus.
For example, a conventional developing cartridge having an electrode for supplying power to a developing roller. The electrode has a shaft that can contact a power-supply section of an image-forming apparatus. This developing cartridge further includes a gear rotatable about the shaft and a protrusion provided on the gear. The protrusion can rotate together with the gear and is configured to contact a lever of the image-forming apparatus. The lever is moved when the protrusion contacts the lever. The image-forming apparatus can detect movement of the lever to thereby determine a specification of the developing cartridge attached to the image-forming apparatus.