TERMINAL CONTROLLING SYSTEM

PURPOSE:To enable an input/output device to select optionally a transmitting destination of a message, by providing a code discriminating an input/output device or a center device to the message which is transmitted to a terminal device from the input/output device. CONSTITUTION:A transmission control code 12 of 2 bits is provided to a part of the messages transmitted from input/output devices 3 and 4. If the value of the 2 bits is equal to 10, a connection route registration message is given to form a connection route between the devices 3 and 4 in accordance with a connecting originator address 13 and a connecting destination address 14. When the value of the code 12 is equal to 01 and 00, an indication is given to transmit the transmission message given from the device 3 to the device 4 and a center device 1, respectively. In such a way, it is possible to select a transmitting destination at the side of the device 3.