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{{Short description|Standard formats for transferring time information}}
'''Inter-range instrumentation group timecodes''', commonly known as '''IRIG timecode''', are standard formats for transferring timing information. Atomic frequency standards and GPS receivers designed for precision timing are often equipped with an IRIG output. The standards were created by the Tele Communications Working Group of the U.S. military's [[Inter-Range Instrumentation Group]] (IRIG), the standards body of the [[Range Commanders Council]]. Work on these standards started in October 1956, and the original standards were accepted in 1960.▼
▲'''Inter-range instrumentation group timecodes''', commonly known as '''IRIG timecode''', are standard formats for transferring timing information. Atomic frequency standards and [[GPS
The original formats were described in IRIG Document 104-60, later revised and reissued in August 1970 as IRIG Document 104-70, upgraded later that year as the IRIG Document to the status of a Standard, IRIG Standard 200-70. The latest version of the Standard is IRIG Standard 200-16 from August 2016.▼
▲The original formats were described in IRIG Document 104-60, later revised and reissued in August 1970 as IRIG Document 104-70, upgraded later that year as the IRIG Document to the status of a Standard, IRIG Standard 200-70.
== Timecodes ==
The different timecodes defined in the Standard have alphabetic designations. A, B, D, E, G, and H are the standards currently defined by IRIG Standard 200-04.
C<ref>{{Citation |url=https://apps.dtic.mil/sti/pdfs/ADA000295.pdf |archive-url=https://web.archive.org/web/20130408112407/http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA000295 |url-status=live |archive-date=April 8, 2013 |format=pdf |title=Special Hardware for ARL Analysis of ACODAC Data |type=technical report |first1=Richard O. |last1=Grohman |first2=Larry L. |last2=Mellenbruch |first3=Felix J. |last3=Sowic |date=1974-03-14 |publisher=Texas University at Austin |id=ARL-TM-74-12 |accessdate=2011-12-23}}</ref><ref>{{Citation |title=Handbook of Time Code Formats |url=http://www.vk7krj.com/ham_stuff_pics/Handbook_of_Time_Code_Formats.pdf |author=Datum Inc. |year=1987 |page=18 |accessdate=2013-06-24}}</ref> was in the original specification, but was replaced by H.▼
The main difference between codes is their rate, which varies between one pulse per minute and 10,000 pulses per second.
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|-
! A
| 1000 Hz || 1 ms || 100 ||
|-
! B
| 100 Hz || 10 ms || 100 ||
|- style="text-decoration:line-through"
! C{{efn-ua|name=CH}}
| 2 Hz || 0.5 s || 120 ||
|-
! D
| {{frac|60}} Hz ||
|-
! E
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|-
! G
| 10000 Hz || 0.1 ms || 100 ||
|-
! H
| 1 Hz ||
|}
{{notelist-ua|name=CH|refs=
▲{{efn-ua|name=CH|C<ref>{{
}}
The bits are modulated on a carrier. A three-digit suffix specifies the type and frequency of the carrier, and which optional information is included:
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<ol start=0 type=1>
<li>[[Direct current|DC]] level shift (DCLS) ([[Pulse-width modulation|pulse width coded]] without carrier)</li>
<li>Sine wave carrier ([[
<li>[[Manchester code|Manchester]] modulated</li>
</ol>
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<li>100 Hz (10 ms resolution)</li>
<li>1 kHz (1 ms resolution)</li>
<li>10 kHz (100
<li>100 kHz (10
<li>1 MHz (1
</ol>
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Thus the complete signal identification number consists of one letter and three digits. For example, the signal designated as B122 is deciphered as follows: Format B, Sine wave (amplitude modulated), 1 kHz carrier, and Coded expressions BCDTOY.
The most commonly used of the standards is IRIG B, then IRIG A, then probably IRIG G. Timecode formats directly derived from IRIG H are used by [[
For example, one of the most common formats, IRIG B122:
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* Bits 10–13 encode minutes, and bits 15–17 encode tens of minutes (0–59)
* Bits 20–23 encode hours, and bits 25–26 encode tens of hours (0–23)
* Bits 30-33 encode [[
* Bits 45–48 encode tenths of seconds (0–9)
* Bits 50–53 encode years, and bits 55–58 encode tens of years (0–99)
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== Sources ==
* {{Citation |last=Telecommunications and Timing Group |publisher=Range Commanders Council |___location=U.S. Army White Sands Missile Range, New Mexico |url=http://www.wsmr.army.mil/RCCsite/Documents/200-16_IRIG_Serial_Time_Code_Formats/200-16_IRIG_Serial_Time_Code_Formats.pdf |format=PDF |id=IRIG standard 200-16 |title=IRIG Serial Time Code Formats |date=August 2016 |access-date=2024-05-27 |archive-date=2018-08-26 |archive-url=https://web.archive.org/web/20180826214654/http://www.wsmr.army.mil/RCCsite/Documents/200-16_IRIG_Serial_Time_Code_Formats/200-16_IRIG_Serial_Time_Code_Formats.pdf |url-status=bot: unknown }}
* {{Citation |last=Telecommunications and Timing Group |publisher=Range Commanders Council |___location=U.S. Army White Sands Missile Range, New Mexico |url=https://wsmrc2vger.wsmr.army.mil/rcc/manuals/212-00/index.htm |format=DOC |id=IRIG standard 212-00 |title=IRIG J Asynchronous ASCII Time Code Formats |date=November 2000 |access-date=2011-10-01 |archive-url=https://web.archive.org/web/20130217171957/https://wsmrc2vger.wsmr.army.mil/rcc/manuals/212-00/index.htm |archive-date=2013-02-17 |url-status=dead }}
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