Identifies the TP which is being switched to. This identifies the TP that is the active source after the switch.
For a 2F BLSR, when the state returns to normal, this is the TP that had switched.
For a 4F BLSR ring switch, when the state returns to normal, this is the worker TP of the span that had switched; for example, if the East span had switched to the West span, then this is the East worker TP.

Readable by NMS? Yes
Writeable by NMS? No
Invariant? Yes
