When reflected pulses return to the antenna, they are directed to the receiver. In the receiver their voltage is amplified by a multiple of several million. This alternating voltage is then converted to direct current and impressed upon a cathoderay oscilloscope. There are a number of electronic methods for converting reflected pulses into visible symbols on a display system composed of advanced data processors and symbol generators. They may be divided into range indicators and plan-position indicators.
Some radar systems use a combination of both types of indicators.
One type of indicator, the A-scope, has an electron beam which sweeps across the oscilloscope screen once in the interval between pulses. In other words, this sweep is made when the antenna is receiving reflected waves. The line of light formed by the sweep is called a time base. The length of the time base corresponds to the range of the radar system. Repeated sweeps of the electron beam maintain the straight line on the screen.