In clock synchronization, holdover refers to what behavior?

In clock synchronization, holdover refers to what behavior?

• A. Synchronizes to an external reference only.
• B. Holdover is maintaining the clock at a fixed rate regardless of the reference.
• C. Holdover maintains timing when the external reference is unavailable.
• D. Holdover stops timing until the external reference returns.

Answer: (C)

Holdover is about keeping time when the external timing reference disappears. When the reference is unavailable, the clock uses its own internal oscillator and the last known timing state to continue advancing time, aiming to stay as accurate as possible until the reference returns. The point is continuity—a clock in holdover keeps running instead of freezing or stopping. Once the external reference is back, the system re-synchronizes. If timing were described as only synchronizing to the external reference or simply running at a fixed rate regardless of the reference, it would miss the key idea that holdover preserves ongoing timekeeping during outages. And stopping the clock would defeat the purpose of maintaining continuous synchronization.

Holdover is about keeping time when the external timing reference disappears. When the reference is unavailable, the clock uses its own internal oscillator and the last known timing state to continue advancing time, aiming to stay as accurate as possible until the reference returns. The point is continuity—a clock in holdover keeps running instead of freezing or stopping. Once the external reference is back, the system re-synchronizes.

If timing were described as only synchronizing to the external reference or simply running at a fixed rate regardless of the reference, it would miss the key idea that holdover preserves ongoing timekeeping during outages. And stopping the clock would defeat the purpose of maintaining continuous synchronization.