Modern radar systems typically use some sort of raster scan display to produce a map-like image. Early in radar development, however, numerous circumstances made such displays difficult to produce. People ultimately developed several different display types.
The radar system transmits a single pulse of electromagnetic radiation, a small portion of which backscatter off targets (intended or otherwise) and return to the radar system. The radar receiver converts all received electromagnetic radiation into a continuous electronic analog signal of varying (or oscillating) voltage.