Stand-alone

Clocks synchronized by a publicly available time reference, such as DCF 77 (German time signal transmitter), or the globally available GPS (Global Positioning System). These clocks do not need any connection to a master clock.
Power supply either by mains or - if feasible - by battery.

Advantages
No installation for the time distribution necessary.
In a range of more than 1500km around Frankfurt, the DCF 77 can be received in most locations, even indoors.

Applications

Stand-alone outdoor clock, powered by mains or battery: railways, municipal clocks in towns, advertising clocks.