 In a radar display, the output signal from the radar receiver is fed into one of three input channels in the oscilloscope.Early displays generally sent this information to either X channel or Y channel to displace the spot on the screen to indicate a return.More modern radars typically used a rotating or otherwise moving antenna to cover a greater area of the sky, and in these cases, electronics, slaved to the mechanical motion of the antenna, typically moved the X and Y channels, with the radar signal being fed into the brightness channel.