Several types of sampling techniques are shown on this slide. Real time sampling is the default mode in most oscilloscopes. It is very good for capturing transient signals, depending on the time base and the number of channels being interleaved, or not. One problem to consider is that it might exhibit problems of aliasing which will be discussed later. Random interleave sampling, also called Equivalent Time Sampling does multiple sampling. It is only to be used for repetitive signals not transients, but it gives a higher effective sample rate. For very low frequency phenomena a good selection is the roll mode.