"Smoothing" a sine wave

Hi everyone, I uploaded an image where in the upper side you can see a product of a sine wave with a series made of a step and a rate limiter... The sine wave in this case represents a noise on the output of the whole system! Professor said that it's a way to make the noise enters by a "smooth way"... Does someone has any idea about this product? What should it produce? What does the rate limiter do on the step? I tried emailing and reading rate limiter and step docs but I haven't been able to solve this problem...