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>{{Citationcite tech report |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 |accessdateaccess-date=2011-12-23 | df = dmy-all }}</ref><ref>{{Citationcite book | title = Handbook of Time Code Formats | url = http://www.vk7krj.com/ham_stuff_pics/Handbook_of_Time_Code_Formats.pdf |author publisher = Datum Inc. | edition = Seventh | year = 1987 | page = 18 |accessdate access-date =2013 2024-0603-18 | archive-url = https://web.archive.org/web/20230308040915/https://www.vk7krj.com/ham_stuff_pics/Handbook_of_Time_Code_Formats.pdf | archive-date = 2023-03-08 | url-status = live | via = vk7krj.com | df = dmy-24all}}</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.
