The first time, Bathys Hawaii, in 2013, introduced Cesium 133 Atomic watch. It was the first watch that keeps time with an internal atomic clock.
Unlike the other radio watches which are corrected by radio time signals and these signals were received from the government atomic clock, this watch contains a tiny cesium atomic clock that places on a chip. In this watch, it is reported to keep time to an accuracy of one second in 1000 years.
This watch is based on a chip developed by the breakthrough chip scale atomic clock (CSAC). The program of the US that is known as (DARPA) as well as the Defense Advanced Research Projects Agency was initiated in 2001 and it produced the first prototype atomic clock chip in 2005.
Such like the other cesium clocks, the watch keeps time with an ultraprecise 9.192631770GHz.
Liquid metal cesium on the chip is a little capsule that is heated to vaporize the cesium.
It also reduces the output of the photodetector. In a phase locked loop, the output of the photodetector is used as feedback which also helps the circuit to keep the oscillator at the exact frequency.
The technology that introduced at that time was coherent population trapping, and it allowed a rack-sized cesium clock to be shrunk small enough to fit on a chip. It played also a very important role to eliminate the need for a bulk microwave cavity.
John Patterson designed the watch. Because the size of the chip was large so the size of the watch was also large. The other problem of the watch was that It must be recharged every 30hours.