Abstract: A modular type image forming system includes a laser printer main unit and a plurality of optional units, such as a both side processing unit, a large quantity paper feeding unit and a mail box unit, each of which is operatively coupled to said main unit through a commonly usable optical fiber cable through a commonly usable connector. Each unit has its own CPU and serial communications between the CPUs of different units may be carried out through the optical cables. The CPU of the main unit may determine the identity of each of the optional units connected thereto through such communications. The main unit also includes an interface circuit through which the main unit is operatively coupled to each of the optional units. The interface circuit includes a port selector which establishes a connection pattern between the main and optional units in accordance with the identity information of each of the optional units connected.

Abstract: A modular type image forming system includes a laser printer main unit and a plurality of optional units, such as both side processing unit, a large quantity paper feeding unit and a mail box unit, each of which is operatively coupled to said main unit through a commonly usable optical fiber cable through a commonly usable connector. Each unit has its own CPU and serial communications between the CPUs of different units may be carried out through the optical cables. The CPU of the main unit may determine the identity of each of the optional units connected thereto through such communications. The main unit also includes an interface circuit through which the main unit is operatively coupled to each of the optional units. The interface circuit includes a port selector which establishes a connection pattern between the main and optional units in accordance with the identity information of each of the optional units connected.

Abstract: A lateral registration adjusting device for use in an optical writing system, such as a laser beam printer, is provided. When a sheet of recording paper has arrived at a registration roller which is driven to rotate intermittently in association with the rotation of a photosensitive drum, a discrepancy between the sheet of recording paper and a reference position in the lateral direction transverse to the direction of transportation of the sheet of recording paper is detected. Based on this information of lateral discrepancy, the writing start position for writing an image on the photosensitive drum in a scan line is adjusted such that the lateral discrepancy is absorbed. Thus, when the image is formed on the drum and then transferred onto the sheet of recording paper, there is obtained a predetermined relative positional relationship between the sheet of recording paper and the image in the lateral direction at all times.