| 摘要 |
PURPOSE:To increase the reliability of the system by securing such state under which the specified terminal unit transmits the return signal by the control signal sent from the master unit and regardless of the operation switch and thus giving a periodical function check to the terminal unit. CONSTITUTION:The signals are transmitted and received in the time-division cyclic multiplex transmission method between the master unit and plural numbers of terminal units, and no return signal is usually transmitted from the terminal. In such system, change-over bit A is given to part of control signal SC sent from the master unit in terms of existence of the return signal, and the rest of the control signal is defined as control data B. Terminalunit 2 extracts bit A by serial-parallel converter 5 to apply it to OR gate G2. At the same time, switch gate signal SWG is supplied to gate G2 from signal process part 6 to be turned to the H level if either one of operation switches 7 is pushed. Then bit A is set at the H level for the control signal sent from the master unit. Thus return signal RET can be transmitted from terminal 2 regardless of switch 7 to lealize a periodical function check for the terminal. As a result, the reliability can be increased for the system. |
