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'''Inter-range instrumentation group time codes''', commonly known as "IRIG" timecodes, were created by the TeleCommunications Working Group of the [[IRIG|Inter-Range Instrumentation Group]], the standards body of the [[Range Commanders Council]]. The workWork on these standards was started in October of [[1956]], and the original standards were accepted in [[1960]].
The original formats were described in IRIG Document 104-60, which was later revised and reissued in August [[1970]] as IRIG Document 104-70, leading to an upgradeupgraded later that year ofas the IRIG Document to the status of a Standard, IRIG Standard 200-70. The latest version of the Standard is IRIG Standard 200-95.
The different timecodes defined in the Standard are givenhave alphabetic designations. A, B, D, E, G, and H are the standards currently defined by 200-95. C was in the original specification, but was replaced by H. The main difference between the codes is their rate, which varies between 1one pulse per second and ten thousand10,000 pulses per second.
* A: 1000 PPS
* B: 100 PPS
The most commonly used of the standards is IRIG B, then IRIG A, then probably IRIG G. Time code formats directly derived from IRIG H are used by [[National Institute of Standards and Technology|NIST]] [[radio station]]s [[WWV]], [[WWVH]] and [[WWVB]].
As anFor example, one of the most common formats, IRIG B122:
IRIG B122 transmits one hundred pulses per second on an amplitude modulated 1 kHz sine wave carrier, encoding information in BCD. This means that 100 bits of information are transmitted every second. The time frame for the IRIG B standard is 1 second, meaning that one data frame of time information is transmitted every second. This data frame contains information about the day of the year (1-366), hours, minutes, and seconds. Information aboutas to which year it is, is not transmitted. [[Leap second]] announcements are not provided. It should be noted that althoughAlthough information is transmitted only once per second, by using a [[phase locked loop]], a device can sychronize its time very accurately with the transmitting device transmittingby using a [[phase locked loop]]. Typical commercial devices will synchronize to within 1 microsecond using IRIG B timecodes.
==Reference==
*[http://www.jcte.jcs.mil/RCC/manuals/200-04/TT-45.pdf IRIG standard 200-04 (PDF)]
[[Category:Synchronization]]
Inter-range instrumentation group time codes, commonly known as "IRIG" timecodes, were created by the TeleCommunications Working Group of the Inter-Range Instrumentation Group, the standards body of the Range Commanders Council. The work on these standards was started in October of 1956, and the original standards were accepted in 1960. The original formats were described in IRIG Document 104-60, which was later revised and reissued in August 1970 as IRIG Document 104-70, leading to an upgrade later that year of the IRIG Document to the status of a Standard, IRIG Standard 200-70. The latest version of the Standard is IRIG Standard 200-95. The different timecodes defined in the Standard are givenhave alphabetic designations. A, B, D, E, G, and H are the standards currently defined by 200-95. C was in the original specification, but was replaced by H. The main difference between the codes is their rate, which varies between 1 pulse per second and ten thousand pulses per second.
A: 10 Khz
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