This paper discusses in detail a new recording methodology invented and patented by IST called Sliding Window Overwrite Mode. This recording mode divides the test period into time windows defined by the user. The number of these windows is also defined by the user. Within each time window the instrument retains the "highest amplitude" g-rms acceleration time histories measured. Using this feature data can be collected over long periods of time and whereby the vibration amplitudes may vary considerably, and still enable capture of some measure of the amplitude(and frequencies) of the vibration data.It also enables the user to compare frequency PSDs of data from different windows to see how they might change over the course of the test.