A replaceable unit is removably installable in an image forming device. The replaceable unit includes a rotatable input gear that is positioned to mate with an output gear of the image forming device. The replaceable unit includes an encoded member that is encoded with identifying information of the replaceable unit and that is operatively connected to the input gear such that rotation of the input gear causes movement of the encoded member. The replaceable unit includes an alignment guide on the exterior of the replaceable unit. The image forming device includes a sensor supported by a sensor housing. The alignment guide is positioned to contact and move the sensor housing during insertion of the replaceable unit into the image forming device to align the sensor with an exposed portion of the encoded member for reading the identifying information from the encoded member by the sensor.