| 摘要 |
PROBLEM TO BE SOLVED: To conduct line control in an excellent way by discriminating propriety of an active line based on a reception signal to control the line based on a result of line quality discrimination. SOLUTION: The controller is provided with a line quality detection section 1A to calculate a line quality index of an active line based on a reception signal, a quality discrimination section 6 to discriminate propriety of a line based on a result of line quality index calculation of the active line obtained from a line quality detection section 1AF, and a control section 7 controlling the line based on the line quality discrimination result by the quality discrimination section 6. Thus, when the result of calculation of the line quality index of the active line to be obtained is less than a threshold level denoting the lower limit of the line quality set in advance, the section 6 discriminates it to be a disable communication state. When the disable communication state is discriminated based on the line quality discrimination result, another line is selected or the line is interrupted. Thus, the line control is conducted in an excellent way. |
