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::::  Decoder for IEN SRC-RAI Hourly Signal
    Galileo Ferraris Torino ::::

A completely digital decoder to microcontroller (PIC 16F628), able to 
decode the Italian official hourly signal transmitted by the IEN-INRIM 
Galileo Ferraris of Torino.
1st full digital Decoder for IEN SRC-RAI Signal !

Galileo Ferraris (1847 - 1897)

Video ! 

The IEN SRC-RAI Signal 





SRC-RAI Signal Test Software   
This is a principal panel in the test software   

The IEN SRC-RAI Signal   


Issue #225 April 2009 

Digital Decoding

Decode Periodic Signal Transmissions

Men have been interested in the topic of time and how to measure it for centuries. Famous philosophers and scientists such as Albert Einstein have studied every aspect of this peculiar physical concept. Through his theory of relativity, Einstein introduced essential concepts about the regular flow of time. These matters continue to puzzle us today. For instance, it is impossible to synchronize two watches that are not in the same “condition.”

Think about the GPS satellites orbiting the Earth at an approximate altitude of 20,000 km. Believe it or not, between the two atomic clocks, one on the satellite and one at sea level, there is a daily difference of about 38.9 µs. It’s a difference we cannot ignore that’s due to different gravitational pulls acting on the orbiting clock and its displacement velocity, which is 12 times greater than the one on Earth. Therefore, GPS satellite systems are usually adjusted before launch in an effort to minimize such effects.

When it comes to time, a temporal scale of reference is important. The old definition of a “second”—as a division of the 86,400 parts of the mean standard day—is inadequate. In 1967, the scientific community acknowledged the new definition of “second.” Back in 1955, English physicians Louis Essen and J.V.L. Parry created the first cesium-beam atomic clock at the National Physical Laboratory in England. In the international system, the “second” then became SI, the duration of 9,192,631,770 periods of the radiation corresponding to the transition between two hyperfine levels of the ground state of the cesium-133 atom.

After that, numerous metrological laboratories adapted to the new technological concept. For instance, since 1970, The National Electrical Institute (IEN) in Turin, Italy, has had its own coordinated universal time (UTC) that is based on cesium-beam atomic clocks. With the introduction of the “cesium fountain” atomic clock in 2003, the Institute, now called The National Institute of Metrological Research (INRIM), has been at the forefront of time measurement. This type of clock has a precision of 10–15, which means a 1-s error in 30 million years, provided that it would work for such a long time.

To coordinate the ever-increasing amount of data produced by the atomic-clock-equipped labs throughout the world, we now refer to the International Bureau of Weights and Measures (BIPM) in Paris, which has calculated the time since 1988 using the UTC times of accredited centers, such as the so-called International Atomic Time (TAI), which has become the scientific community’s official point of reference for time measurements.

In this globalized, computerized world, we cannot ignore the importance of having a universal temporal scale of reference. Think about the financial and stock transactions that are quickly transferred through the telecommunication networks and may change their values in only seconds. Time synchronization is important in everyday life as well. If you think I am exaggerating, let’s go back for a moment to New Year’s Day 2000 when a simple time change was supposed to trigger a world-wide catastrophe. Fortunately, no big problems occurred. But to prevent a potential catastrophe, numerous tests were conducted on devices for thousands of hours.

Today, many systems are automatically synchronized through Network Time Protocol (NTP) servers on the Internet. To supplement its divulgation activities, the INRIM has two NTP free access servers, which are set with the institute’s UTC-IEN time. These servers are found at the following addresses: ntp1.ien.it ( and ntp2.ien.it (

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