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Appendix B
IRIG Protocol Overview
©
National Instruments Corporation
B-3
NI PXI-6682 User Manual
For pulse width modulated systems, conventional digital binary signaling
is used, and mark is defined as the logic high state, while space is defined
as the logic low state.
For amplitude modulated systems, the source must generate sinusoidal
signaling modulating the amplitude such that it has a 10:3 mark:space
amplitude ratio (the range of allowable mark to space ratios is 3:1 to 6:1).
The source must phase align the generated sine wave such that the leading
edges of bits are coincident with zero crossings of the sine wave.
Figure B-1 shows an example of transmission of a binary one, a binary
zero, and two position identifiers (with the second’s boundary at the leading
edge of the second position identifier). The figure shows the information
transmitted using an amplitude modulated signal, and a pulse width
modulated signal.
Figure B-1.
IRIG-B AM and DC Transmission Example
IRIG-B is one of the most common IRIG standards used. The following
table describes how the information is transmitted when using IRIG-B each
second.
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