In 1872, Xujiahui Observatory grew out of the Zi-Ka-Wei observatory which was established by the French Catholic Jesuit Church in Shanghai. It began to work in time service in 1884. Initially, artillery was used for timing, firing at 2 pm on Monday and Friday. After the completion of the Bund signal tower, the hanging electric ball was used instead, and the standard time was reported by falling ball at 12 noon and flashing at 9 PM.

Xujiahui Observatory in 1900(left) and 2019(right) (Image by Shanghai Astronomical Observatory, CAS)

In 1914, the radio time signal station was established in Shanghai which broadcast radio time signals by manual keystrokes.

In 1926, it began to carry out astronomical time determination through meridional and transit instruments. International time signals were broadcast at 11am and 5pm every day, with call sign FFZ.

Time Ball on on the Bund of Shanghai in 1920s (Image by Shanghai Astronomical Observatory, CAS)

In 1940, the scientific time signal was broadcast with an accuracy of about 10 milliseconds.

In 1950, the astronomy and time service parts of Xujiahui Observatory were assigned to Purple Mountain Observatory. The international and scientific time signs (call sign: XSG) were broadcast on four frequencies by coastal radio, and the broadcast time was extended to 11:00, 17:00, 19:00, 21:00 and 23:00 successively.

From midnight on July 1, 1954, Xujiahui Observatory rented a 5kw transmitter of Shanghai Zhenru International Communication Station to broadcast time signals (call sign BPV) at 19:00, 21:00 and 23:00 every day. This was the first time that China has its own time signals, broadcast with BPV call sign, and had appeared in 40 radio time signals worldwide.

In 1956, the broadcast of the mean-time type time signal was added, meanwhile, the power of broadcast was gradually increased, and other time periods, such as 1:00, 3:00 and 5 :00, were added to start broadcasting.

In 1962, Shanghai Observatory was established with the combination of the Xujiahui Observatory's astronomical time part and the Sheshan Observatory.

TIPS : What is the time signal and call sign?
Time signal: Signal which represent specific time scales sent by radio through timing station with a certain frequency and format in a certain period of time, is called radio time signal (time signal for short). The old type time signal generated the second signal by the keying method through the automatic control equipment. According to the signal format, there are ONOGO type time signals, scientific type time signal and mean-time type time signals. The new time signal refers to the pulse time frequency signal generated by the frequency modulated carrier from the frequency source.

Call sign: It is the legal codes of radio stations which is unique all over the world. China's radio time signal station and call signs include BPV short-wave time service station (discontinued in 1981), BPM short-wave time service station, BPL long-wave time service station, and BPC low-frequency time-code broadcasting station and so on.