A line outage is what you get when a transmission line is not available for a certain period of time. For a line to be considered to be available, it has to be pasasing traffic in both directions and should be reasonalby error-free.
A line gets synchronization errors possibly as a result of clocking misconfiguration. When that happens, the end-device is not able to read data off the line at the same intervals that the sending device is placing them on the line.
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Paresh
