PURPOSE: To increase the processing efficiency of both a central control device and a data channel device, by performing an automatic type-out of the fault information stored in a memory within an I/O control unit and through this control device after receiving a fault information type-out instruction from the central control device.

CONSTITUTION: A type-out command of the fault information of an electronic switchboard is given to an I/O control device 7 from a CPUCC1 via a data channel device 2. Then the instruction is discriminated by an instruction discriminating circuit 3. In this case, if the instruction is equal to a fault information type-out instruction, a control circuit 4 selects the fault information of the term number designated by a device out of the faults stored in a memory 5. Then an interface action is finished between the devices 2 and 7 at the moment when the selection of fault information is over. Thus the device 7 transfers the selected fault information to a typewriter 6. Then the device 7 reports the type-out of fault information to the device 2 when the fault information is typed out.