Importance

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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. When paper is fed into a transportation path, paper ID is assigned to the paper and retained until the paper is discharged. If the paper is removed from the path without passing a predetermined location, the same image is printed again.

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First Claim