Casio Wave Ceptor
The Casio Wave Ceptor is a line of radio watches by Casio. Wave Ceptor watches are able to calibrate themselves to the correct time by receiving time signals from various government time services around the world. These signals are normally driven directly by ultra-accurate atomic clocks, and so by synchronizing with the signals, the Wave Ceptor watches achieve long-term accuracy - nearly the same accuracy as the atomic clocks that drive the time signals, which is on the order of one second in three million years.
The Wave Ceptor watches are not the only radio-controlled wristwatches on the market. The German manufacturer Junghans and Japanese manufacturer Citizen Watch Co. also have this feature. Like most radio-controlled watches, the Wave Ceptor watches require no setting or resetting of time, date, daylight saving time, or year; and like most other watches of this kind, they synchronize at least every 24 hours, usually in the middle of the night. Their long-term and short-term accuracy is thus better than 500 ms.
As with all radio-controlled watches they revert to free-running quartz accuracy in areas out of range or shielded from time setting signals. The time setting signals usually come from radio emitting towers. However, they are still as accurate as other quartz watches in this mode.
The receivers to which the watches can tune themselves vary by watch submodel. CASIO mentions that in Europe, the watches will tune to the low frequency time signal radio station DCF77 located at Mainflingen in Germany or MSF at Anthorn (formerly transmitting from Rugby, Warwickshire) in the United Kingdom. In Europe the reception range is approximately 1500 kilometres. In the United States, they will tune into WWVB at Fort Collins. In Japan, they will tune to JJY on 40 kHz Mount Otakadoya, and 60 kHz Mount Hagane. In China, they will tune to BPC at Shangqiu. Some watches can register only some of these signals.