| 摘要 |
PROBLEM TO BE SOLVED: To obtain a stable count of error seconds by correcting an error due to a difference from clock sources caused steadily in the case of counting error seconds from quality information of a subscriber channel in a subscriber interface of an ATM transmission system. SOLUTION: A subscriber interface panel 30 of the ATM transmission system has a specified second counter 31 that controls a fixed period, an error second counter 32 that counts error seconds, a counter 33 that counts the error seconds, and a correction device 34 that corrects the error second counter 32. A DSU 40 installed in a subscriber's home uses an error detector 41 to measure channel quality of a subscriber line and gives the result to the subscriber interface panel 30. The error second counter 32 of the subscriber interface panel 30 counts the number of errors of section channel quality information for a fixed period and the correction circuit 34 corrects the count based on an error second count corresponding to the count of the counter 33.
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