As of 2015, Casio is the only brand of atomic solar watches. It offers the G-Shock, Pro-Trek and Edifice series of watches that feature atomic timekeeping and solar-powered batteries.
The atomic timekeeping function uses radio signals to receive time calibration signals, keeping the watch synchronized with one of several worldwide atomic clocks, such as the NIST-F1 U.S. atomic clock in Boulder, Colorado.
These watches also features a miniature photovoltaic panel behind the face that charges the battery in direct sunlight, precluding the need to replace batteries frequently. Watch functions drain the battery over time and require this exposure to continue full use.
Other features included with some, but not all of Casio's watch brands include resistance to shock, water immersion to a certain depth, extreme temperatures or magnets. Some timepieces also feature manual or automatic LED backlights to illuminate the clock face in dark situations. Others offer a GPS or Bluetooth synchronization feature in lieu of radio-frequency updates.
Certain models of the Pro-Trek series of Casio watches feature non-timekeeping instruments such as a combination barometer and altimeter, thermometer and compass. These are useful in a variety of situations where access to the information these instruments provide is otherwise unavailable. The line is primarily designed for outdoor use.