Indicates whether or not the timing source at the far-end node is
traceable to a Primary Reference Clock.
The timingMarker indication is controlled by the timing marker bit
in the G832 MA byte. If the received timing marker bit is 1 for five
consecutive frames, and five consecutive 0s are not received for two
seconds, the timingMarker indication will be set to not traceable. If
the received timing marker bit is 0 for five consecutive frames and
five consecutive 1s are not received for two seconds, the
timingMarker indication will be set to traceable.