1. A character recognition communication system comprising: a plurality of terminals, each terminal including a general-purpose facsimile unit having a scanning means for transmitting characters on a document medium as image signals; at least one center for receiving a message which includes character codes to thereby effect output processing and data processing; and a communication network connected between said message receiving center and said terminals for receiving the image signals from the terminals, recognizing characters, constructing a message according to the result of character recognition and transmitting said message to the message receiving center designated by an address data included in the result of character recognition, said communication network comprising: a switching device for switching the image signals from said terminals and transmitting the same to said message receiving center; a character recognition unit coupled to said switching device for recognizing characters; a recognition control unit coupled between said switching device and said character recognition unit for controlling said character recognition unit to recognize characters from the individual image signals from said terminals, said recognition control unit comprising: an image signal receiving unit for receiving said image signals from said terminals and for delivering image signals and control signals necessary to achieve character recognition; an image signal converting unit for converting the image signals from said image signal receiving unit to binary output signals, the values of which are controlled by said control signals from said image signal receiving unit, said image signal converting unit generating a completion signal representing completion of conversion of said image signals; a memory having addresses any one of which stores said output signals of said image signal converting unit as an image pattern; a communication control unit for causing, in response to said completion signal from said image signal converting unit, said character recognition unit to recognize the image pattern stored in an address of said memory, storing the result of image pattern recognition to thereby construct the message, and transmitting the message to the message receiving center designated by an address data included in the result of image pattern recognition; and transmitting and receiving means for operating said switching device to connect said recognition control unit to said terminals or to said message receiving center by means of an interconnecting line.