As a result, errors caused by spatial orientation and positioning become less of a concern. Besides that AT-cut variations allow for greater temperature tolerances, specifically in the range of −40 to 125 ☌ (−40 to 257 ☏), they exhibit reduced deviations caused by gravitational orientation changes. Key elements to obtain the high claimed accuracy are applying a for a watch unusual shaped ( AT-cut) quartz crystal operated at 2 23 or 8 388 608 Hz frequency, thermal compensation and hand selecting pre-aged crystals. In 2018 Citizen announced it developed the Caliber 0100 Eco-Drive prototype autonomous high-accuracy quartz watch movement which is claimed to be accurate to ± 1 second per year. This watch features a ring-shaped solar cell surrounding the watch case sidewall. In 2012 Citizen announced the Eco-Drive RING Concept Model. This makes radio-controlled timing possible in remote areas that are not serviced by land based radio time signal stations. The Concept Model 2011 was the Eco-Drive SATELLITE WAVE that has a movement that can receive time synchronization signals from GPS satellites. These Eco-Drive Concept Models are generally shown at exhibitions and produced in limited editions. Since 2009, Citizen has developed Eco-Drive Concept Models as technology demonstration and marketing tools. This is a very large watch, the titanium watch case has a diameter of 52.2 mm and thickness of 22 mm and features a helium release valve, designed for mixed gas saturation diving at great depths.
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Later specialized tool watch designs were introduced like the Promaster Eco-Drive Professional Diver 1000M Titanium BN7020-09E in 2017. During the mid-2000s, wristwatch sales improved for Citizen thanks to further development of the Eco-Drive line and integration of radio-controlled timing with the 2002 Eco-Drive line. In 2002 the VITRO technology (Eco-Drive VITRO) came on the market, where the solar cells were no longer even slightly visible under the dial. Eco-Drive models were well received, generating a third of Citizen's North American revenues by 2000. In the early 2000s, while wristwatch sales declined with the advent of cell phones and their timekeeping capability, demand for Citizen watches in North America remained robust. Where the first models offered hours, minutes, seconds and date features, ultimately the movements evolved to include a broad range of design features, including complex analog and digital-analog movements and the horological complications of chronographs, flyback chronographs and dive watches. In addition to the first three Eco-Drive models introduced in 1995, Citizen marketed numerous other Eco-Drive models during the 1990s, including the 6.05 mm (0.238 in) thick Eco-Drive Slim of 1996. The accuracy of the quartz movement was stated as within ± 20 seconds per month at a normal temperature range of 5 to 40 ☌ (41 to 104 ☏).
The movement also featured an "insufficient recharging" indicator. This battery type became available in the early 1990s, enabling an Eco-Drive 7878 movement to run 180 days on secondary power before requiring recharging via light exposure – a marked improvement in energy storage over previous light-powered watches. To store electrical energy the first Eco-Drive movements employed titanium lithium-ion rechargeable or secondary batteries. Though the Eco-Drive caliber 7878 movement solar cells remained slightly visible through the dial, the physical styling of the light-powered watch was no longer constrained by visible solar cells. By locating a sufficiently translucent dial material over the now more efficient solar cells, enough light could pass through the dial face to power the movement. This innovation was enabled by marked improvements in thin film amorphous silicon solar cells, which, by the early 1990s had become significantly more efficient. Previous light powered watches from Citizen and other manufacturers had the solar cell(s) mounted directly on the dial. This movement was the first light-powered movement where the solar cells could be mounted under the dial. The technical platform that made the Eco-Drive concept possible was the Eco-Drive caliber 7878 movement.