Casio Radio Controlled Watches

The exact time, without you having to adjust it. Automatic synchronization via atomic signal.

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Atomic precision · Automatic synchronisation · Casio

Radio Controlled

The exact time, without you having to set it

Watches that set themselves

Casio's radio controlled watches receive a time signal broadcast from atomic transmitters located in different parts of the world. That signal contains the exact time, and the watch adjusts automatically to it without you having to do anything. It's not a feature that only activates when you travel: the watch synchronises every night while you sleep, and if reception is good, you wake up with the exact time on your wrist.

The technology relies on caesium atomic clocks, which are what set the official time reference in each region. The watch doesn't carry one inside, but it receives its signal and adjusts its mechanism accordingly. It's the most accurate way to wear a watch without having to worry about drift of a few seconds.

Atomic time signal Automatic synchronisation Tough Solar World time

Multiband 6, Tough Solar and automatic correction

Most of Casio's radio controlled models use the Multiband 6 system. This means the watch can receive signals from six transmitters located in Japan, the United States, the United Kingdom, Germany and China. Depending on the home city you've set, the watch automatically selects the most suitable signal. Reception takes place up to six times a day, usually at night, which is when conditions are most favourable.

Many of these watches also include Tough Solar, Casio's solar charging system, which converts light into energy to power the movement. The combination of both technologies is what makes these watches practically self-sufficient: you don't need to change the battery or set the time.

Frequently asked questions

What happens if I travel to a country where the signal doesn't reach?

The watch keeps running, but it stops receiving the calibration signal. In that case, the watch's accuracy depends on its internal movement, which usually keeps a margin of error of a few seconds per month. When you return to an area with coverage, the watch will resume automatic synchronisation. If the place you're in doesn't have coverage but the home city you've set does, you can try a manual reception by holding the watch near a window.

Why does reception sometimes fail?

The time signal is a low-frequency radio wave, and like any radio signal it can be affected by its surroundings. Buildings, mountains, electrical interference or even weather conditions can make reception difficult. That's why the watches attempt synchronisation several times during the night, when there's less interference. If it fails one night, it doesn't matter: it will try again the next day.

Is the time it shows exactly the atomic time?

The watch receives the signal, processes it internally and adjusts its hands or display accordingly. That calculation process can introduce a minimal margin, of less than a second, between the atomic time and the time the watch shows. In practice, it's an imperceptible difference, but it's worth knowing that the watch isn't the atomic clock itself, but a receiver of its signal.

Do I need to set anything for it to work?

Just one thing: the home city. The watch needs to know which time zone you're in so it can select the appropriate transmitter and apply the correct offset. Once that's set, reception and adjustment are automatic. If you change time zone permanently, you'll need to update that setting manually.