GE P4A Technical Manual page 85

P54A/B/C/E
If, for example, Device A is transmitting to Device B information about the value of its measured current, the
information Device A is receiving from Device B about the current measured at the same time, may reach device B
at a different time. This has to be compensated for. A 1pps GPS timing signal applied to both devices will help the
IEDs achieve this, because it is possible to measure the exact time taken for both transmission and receive paths.
Note:
The 1 pps signal is always supplied by a GPS receiver (such as a P594).
Note:
This signal is used to control the sampling process, and timing calculations and is not used for time stamping or real time
synchronisation.
P54xMED-TM-EN-1
Chapter 3 - Hardware Design
59