A giant clock on a tower face does not rely on a caretaker with a key. It runs from a quartz oscillator, the same basic component inside a wristwatch or phone. When electricity passes through a cut of quartz crystal, it vibrates at a fixed resonant frequency, forming a highly stable timebase that counts seconds and drives stepper motors behind the hands.
To stop that crystal from drifting, the control electronics listen to long‑range radio time signals that are themselves locked to an atomic clock defined by cesium hyperfine transition. A decoder reads the encoded time code, compares it to the local quartz time, and applies phase‑locked loop corrections. Tiny adjustments in frequency and phase keep the displayed time aligned with Coordinated Universal Time without physical winding.
Power supplies with voltage regulation and temperature compensation maintain stable conditions, reducing frequency shifts in the quartz resonator. Backup batteries bridge short outages so counters and dividers do not lose track. Gear trains and bearings simply follow electrical impulses; they do not set the time. As long as the radio transmitter and local electronics stay active, the large hands continue to track atomic standards.
