Automation systems located in different places can be synchronized in different ways. During a time slot process, synchronization can be deduced from the cyclical protocol. The synchronization process is based on the transmission of a synchronization signal which is cyclically received and analyzed by all network devices. In order to be able to ensure the best possible synchronization, the signal has to be sent and received within a strict time period with the lowest possible time discrepancy.
Another way of increasing the Ethernet’s temporal precision and synchronization is based on the principle of separate clocks (IEC 61588) which are synchronized with each other via telegrams. Separate clocks allow for a precise time base that is not affected by transmission time and time fluctuations in the communications medium. However, since the time base is not able to ensure any determinism when transmitting data, the data always has to be transmitted long enough in advance so that it is available to be processed when it is time for synchronization. Separate clocks are also used in some real-time Ethernet protocols to minimize jitter during cyclical transmission.