via an app and allows it to upload log data in the phone, download map information from the phone and also synchronise itself with the phone in order to keep perfect time. The watch comes without a replaceable battery. The battery is either charged by solar cells present on the face of the watch (called Tough Solar by Casio) or via a wireless charger supplied with the watch, a first for a Casio watch. In 2019, Casio released the GA-2100 which took design inspiration from the original DW-5000C but now incorporated an analog-digital display. Due to the octagonal bezel shape bearing a strong resemblance to the Audemars Piguet Royal Oak, the watch was nick-named "CasiOak" by fans. The use of the carbon reinforced plastic in the watch case allowed the watch to have a thickness of 11.8 mm, making it the thinnest G-Shock available as well as the lightest analog digital model with a weight of 51 grams. The aforementioned characteristics allowed the model to achieve increased popularity among collectors. A solar powered model with Bluetooth time reception capabilities called the GA-B2100 was released in 2022. Multi-Band 6 The Multi-Band 6 is a radio control technology first introduced on the GW9200 Riseman in 2008 and is a successor to the Multi-Band 5 (which supported synchronisation with 5 atomic time transmitters around the world) and Wave Ceptor (which supported synchronisation with atomic time transmitters present in the United States and Japan only) technologies. G-Shock watches with Multi-Band 6 technology can synchronise with one of the six atomic time transmitters in the world in order to keep accurate time. The following is a list of the six atomic time transmitters: Japan Watches can tune in to two locations: The 40 kHz signal from JJY at Mount Otakadoya, near Fukushima (Ohtakadoyayama). The 60 kHz signal from the Haganeyama Transmitter at Mount Hagane (Haganeyama). China Watches tune to the 68.5 kHz signal from BPC at Shangqiu. This is the newest additional signal; older multi-band 5 watches will not be able to connect to this signal, and must be upgraded to a newer multi-band 6 watch in order to synchronise from there. United States Watches tune to the 60 kHz signal from WWVB at Fort Collins. United Kingdom Watches tune to the 60 kHz MSF at Anthorn. Germany Watches tune to the 77.5 kHz low frequency time signal radio station DCF77 at Mainflingen. Guinness World