 but just know that there will be a formal definition. Figure 3-7 illustrates the jitter effect. Being short-term variations in the signal, jitter can be filtered out, or mathematically smoothed, SO that the input timing signal is followed only for longer-term trends and each short-term variation is not immediately used to update the state of the local oscil- lator. Obviously, if these short-term offsets are too large, it creates a problem in sampling, decoding, and recovering time information. Significant instants Ideal signal Jitter Jitter Jitter Signal with jitter Figure 3-7 Phase Fluctuations-Jitter Wander, on the other hand, is a longer-term effect and SO cannot easily be ignored. A slave clock receiving a timing signal from a master clock cannot decide to "second guess" the accuracy of the data from the master clock and ignore (within limits) the input. That is a very dangerous assumption to make, as the whole point of a timing network is to transport a more accurate clock to the slaves with poorer accuracy. The only exception is if the input is completely out of the range of expected values and beyond the tolerance of the slave clock. Figure 3-8 gives an illustration of wander in a timing signal, showing the lower signal first lagging on the upper signal before running ahead of it (indicated by arrows). Note that because time is in- creasing to the right on the horizontal axis, the significant instant moved to the right is behind and not in front of the other signal. Figure 3-8 Phase Fluctuations-Wander Every time-sensitive application has its own defined minimum requirement around phase accuracy for smooth operation. You can define the requirement in several ways: The maximum allowed offset from a reference clock An offset between master and slave clocks A relative offset between two slave clocks Therefore, it is important to track these variations and use mechanisms to minimize or partially re- move errors from the timing signal. To this end, the standards define performance parameters for various measur