PURPOSE: To dispense with the forming of a terminator out of metal or by mold, and to reduce the cost, by connecting a termination resistance internally to an electron apparatus at the termination, automatically.

CONSTITUTION: The A connector for in-line connection has three pins, and its A and B terminals are connected to signal lines 22 and 23 at the inside respectively. A GND terminal is earthed through an internal signal line 24 and a resistance 25 for standard potential. The B connector has also three pins in the same manner. Since a cable is not connected to the B connector at the inner side of an electron apparatus group connected in-line, a microswitch 28 is closed, and a termination resistance 29 is connected automatically. In the electron apparatuses other than the electron apparatuses at both sides, of the electron apparatus group connected in-line, the cable is connected to the B connector, the switch 28 is opened, and the resistance is made in the released condition. As a result, the laying work of the electron apparatus through a communication wire is simplified.