7 Introduction: Abstract of Time Code
7 Introduction: Abstract of Time Code
The transmission of coded timing signals began to take on widespread importance in the early 1950´s. Espe-
cially the US missile and space programs were the forces behind the development of these time codes, which
were used for the correlation of data. The definition of time code formats was completely arbitrary and left to
the individual ideas of each design engineer. Hundreds of different time codes were formed, some of which were
standardized by the "Inter Range Instrumentation Group" (IRIG) in the early 60´s.
Except these "IRIG Time Codes" other formats, like NASA36, XR3 or 2137, are still in use. The board &PROD-
UCT however only decodes IRIG-A, IRIG-B or AFNOR NFS 87-500 formats. The AFNOR code is a variant of
the IRIG-B format. Within this code the complete date is transmitted instead of the "Control Functions" of the
IRIG telegram.
7.1 Description of IRIG-Codes
The specification of individual IRIG time code formats is defined in IRIG Standard 200-04. They are described
by an alphabetical character followed by a three-digit number sequence. The following identification is taken
from the IRIG Standard 200-98):
character bit rate designation A 1000 pps
B 100 pps
1st digit form designation 0 DC Level Shift pulse width modulated
1 sine wave carrier amplitude modulated
2nd digit carrier resolution 0 no carrier (DC Level Shift)
1 100 Hz, 10 msec resolution
2 1 kHz, 1 msec resolution
3 10 kHz, 100 µsec resolution
3rd digit coded expressions 0 BCD(TOY) , CF, SBS
1 BCD(TOY) , CF
2 BCD(TOY)
3 BCD(TOY) , SBS
4 BCD(TOY) , BCD(YEAR) , CF, SBS
5 BCD(TOY) , BCD(YEAR) , SBS
6 BCD(TOY) , BCD(YEAR)
7 BCD(TOY) , BCD(YEAR) , SBS
———————————————————————————————————————–
BCD: time of year, BCD-coded
CF: Control-Functions (user defined)
SBS: seconds of day since midnight (binary)
SyncBox N2X Date: 17th September 2019 23
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