The numerical relays scheme it is often desirable to synchronize the relays real time clock so that events from different relays can be placed in chronological order. This can be done using the IRIG-B.
it is an order that can be fitted to provide an accurate timing reference for the relay. This can be used wherever an IRIG-B signal is available.
The IRIG-B signal is connected to the board on the back of the relay. The timing information is used to synchronize the relay’s internal real-time clock to an accuracy of 1 ms.
It’s Real time clock/time synchronization - time synchronization possible from IRIG-B.