Preprocessors in a data communication computer environment

Realizing the need for a highly adaptable transmission control unit to interface varied terminal equipment to the Michigan Timesharing System (MTS), the University of Michigan initiated in 1965 the development of a special control unit to be used in conjunction with the System/360 Model 67. Called the Data Concentrator The design approach taken in the Data Concentrator has been to nucleate about a small general-purpose computer a number of special-purpose interfaces to the various data set equipment. An integral part of the design is an interface which connects directly to the Model 67 multiplexor channels on one hand and to the Data Concentrator computer on the other. This approach avoids the operational restrictions imposed by an off-the-shelf IBM control unit to interface the two machines. In the next section several points will be raised concerning the design goals of this equipment, concerning general characteristics desirable in any terminal control unit and supporting supervisory system. Following this is a detailed description of the Data Concentrator hardware and an overview description of its supervisory program system. Much of this material has appeared in [3 and 6].