l observation intervals. This means that if a higher value of MTIE is measured for subsequent observation intervals, it is recorded as a new maximum or else the MTIE value remains the same. This in turn means that the MTIE values never decrease over longer and longer observation intervals. For example, if the MTIE observed over all the 5-second periods of a measurement run is 40 ns, then this value will not go to less than 40 ns when measured for any subsequent (longer) periods. For example, any MTIE that is calculated using a 10-s period will be the same or more than any maximum value found for the 5-s periods. This applies similarly for larger values. Therefore, MTIE can only stay the same or increase if another higher value is found during the measurement using a longer observation interval; hence, the MTIE graph will never decline as it moves to the right (with increasing tau). The MTIE graph remaining flat means that the maximum peak-to-peak delay variation remains con- stant; or in other words, no new maximum delay variation was recorded. On the other hand, if the graph increases over time, it suggests that the test equipment is recording ever-higher maximum peak-to-peak delay variations. Also, if the graph resembles a line increasing linearly, it shows that the measured clock is not locked to the reference clock at all, and continually wandering off without correction. MTIE is often used to define a limit on the maximum phase deviation of a clock signal. A simplified algorithm to record and plot MTIE is explained as follows: 1. Determine all the TE values for every 1-second interval (the values may have been sampled at a higher rate, such as 1/30 of 1 second). 2. Find the maximum peak-to-peak delay variation within each observed 1-s observation interval (MTIE values for 1-s intervals). 3. Record the highest value at the 1-s horizontal axis position in the MTIE graph. 4. Determine all the TE values for all 2-s intervals. 5. Find the maximum peak-to-peak delay variation within each observed 2-s interval (MTI