Radio-controlled timepieces

The radio-controlled timepiece displays the precise time and calendar by automatically receiving a radio signal on an official standard frequency. 
There are two types of radio-controlled timepieces. One is a radio-controlled watch (operates in any position and is designed to be carried or worn) and another is a radio-controlled clock (designed to be used in a fixed position).

The mechanism of the radio-controlled timepiece for displaying precise time is as follows. 
The antenna inside the case or band of the timepiece automatically receives the time signal of the Japan Standard Time (JST) transmitted on the official standard frequency which includes time and calendar information at regular time intervals to adjust losses or gains and display the precise time. The JST is based on a "Cesium atomic clock" that may gain or lose 1 second over the course of 100,000 years.
A time signal on the standard frequency sent by a transmitting station is received by the antenna and sent to the receiver of the timepiece. The signal is amplified in the receiver and the receiving pulse is sent to the microprocessor. The microprocessor decodes the time signal, and adjusts the timepiece and displays the precise time automatically. 
After having received a time signal, the timepiece runs as accurate as an ordinary quartz timepiece.
The standard frequency in Japan is operated by the National Institute of Information and Communications Technology (NICT) (, and transmitted from the Fukushima standard frequency station (Ohtakadoyayama) and Kyushu standard frequency station (Haganeyama).
Since commencing transmission of the standard frequency from Fukushima station in June 1999, transmission power has been strengthened from 10kW to 50kW, and the reception range has expanded to approximately 1,200 km from the station. In October 2001, transmission from the Kyushu station commenced allowing the standard frequency to be received across the entire country.
Currently, a study for providing a variety of information including news and emergency information, as well as time information, using the standard frequency, is underway.

Detailed drawing of antenna block

(Note): The above information applies to the members of
the Japan Clock & Watch Association and their products.