This entry indicates the source the nodal timing is locked to. none - is an invalid option for Master clock. internal - is an invalid option for Fallback clock . station - is an invalid option for a stand-alone unit. lbt - loop-back timing ntr - A system locked reference clock adaptive - clcok locking is achieved by altering the clock according to the data load notApplicable - for ML source of Kmux or ML Timing combinations when Master/Fallback clock are not applicable.