Abstract: Circuitry for displaying a constantly changing M-mode transducer scan output on a raster scan display in the form of a first multiplicity of data lines each containing a second multiplicity of data words and each representing a scan of the transducer output at a particular closely spaced scanning time and such that the data line representing the oldest scan is periodically erased and a data line representing the newest scan is displayed. The circuitry includes random access memory having a first multiplicity of memory elements each for storing a data line. A random access memory input counter enables loading of the memory, data line by data line, and a random access memory advance output counter enables read out from the memory sequentially one data word from each line for each raster scan.