This reports the timing reference source the system had to be forced onto, distinct from a normal preference-based selection, typically indicating none of the higher-quality or preferred sources in the group were usable at that moment. Seeing this object populated, rather than empty or matching the preferred/selected reference, is itself a signal to an admin that the protection group has degraded to an exception condition rather than operating under normal automatic selection logic. For example, this might show the device's own internal oscillator name if all external timing references in the group have failed and the system has been forced onto its free-running local clock.