| 摘要 |
PROBLEM TO BE SOLVED: To reduce occurrence of data re-transmission and a communication error by setting an optimum communication rate depending on an acquired state of a real line. SOLUTION: A ROM 2 has a plurality of speed tables 21, 22, 23 with different characteristics storing data where eye quality monitor EQM values, and optimum transmission rates used for data transmission are in cross-reference with each other. Any of the speed tables 21, 22, 23 is selected and stored in a RAM 71 of a modem 7 as a speed table 72 that is used of deciding an actual communication rate on the condition that a communication error or a PPR occurs in the actual communication or the like under the control of a main control section 1. Thus, a communication unit corrects a communication rate decided by a table arithmetic operation using the speed table in response to a state of the real line to which the communication unit is installed on the basis of the actual communication result.
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