About the IRIG Output Resolution
The IRIG output signals are generated from VersaSync's System Time, which can be synced to one or more external input references (such as GPS, IRIG, PTP, etc). The accuracy of the System time to true UTC time is dependent upon what the selected external reference is (with GPS typically being the most accurate reference for the system to sync with).
As for the four available IRIG outputs of the 1204-15 Option Card, outputting an IRIG DCLS (Phase Modulation) signal provides much better and more accurate synchronization of another device than does an IRIG AM (Amplitude Modulation) signal. This is due to the faster rise-time with the DCLS signal being able to provide a more “crisp” on-time point (more distinct, with less jitter) than the slower rise-time of an AM modulated signal.
IRIG AM synchronization of a device to its IRIG source is typically measured in the tens of microseconds, while synchronization using a IRIG DCLS signal can typically provide around 100 nanoseconds or so (plus the cable delays between VersaSync and the other device, as well as the processing delays of the other system itself).
Note that each of the four IRIG outputs of the Model 1204-15 card has its own available ‘offset’ capability, which is configurable via VersaSync’s Web UI, to help account for cabling and processing delays of the device each output is connected with.