Abstract: A casing is intended to meet various requirements of a computer network system, reduce the cost of a computer network system, enable the enhancement of a computer network system after installation, and secure desired functions and reliability of a computer network system for a long period of use. The casing is constructed by stacking a plurality of types of subordinate casings (2, 3) differing from each other in height on a base (4). Each of the subordinate casings (2, 3) is provided with an individual front cover (5), and common signal lines on its rear surface having removable rear cable covers on the rear surface. The subordinate casings (2, 3) contain general-purpose electronic devices, such as a personal computer, a workstation, an extension disk/disk array, an integrated communication server (ICS), an uninterruptible power supply and the like, respectively. The functional devices are interconnected by signal lines extended on the rear surface of the casing to construct a system.

Abstract: A communication control system arranged between a plurality of terminal apparatuses and a host processing unit in order to transmit and receive signals based on an NRZI coding system between them by way of a half duplex communication system, a "0" bit detecting circuit for detecting the "0" bit of a one-bit length is provided in the communication control system and the sending and receiving modes are automatically switched in accordance with the output of this detecting circuit.