TU pointer adjustment event

Question:
Does a TU pointer justification event detected on a lower-order channel of the local station mean pointer justification on the local station? Why?
Answer:
When the local station detects a TU pointer justification event on a lower-order channel, it does not mean that pointer justification occurs at the local station. Instead, it means that pointer justification occurs at the remote station corresponding to the lower-order channel. Pointer justification occurs during lower-order channel multiplexing into the AU. To be specific, pointer justification occurs in upstream signals. However, pointers are explained in downstream signals, or at the receive end. Therefore, the pointer justification at the local station can be detected only at the remote station. When the local station detects a pointer justification event, the pointer justification occurs at the remote station.

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