 Each receiver antenna was sent to one of the channels of the displays in turn , causing one of the displays to refresh . For instance , at a given instant the switch might be set to send the signal to the left side of the azimuth display . The timebase generator was triggered to start sweeping the CRT dot up the screen after the transmission ended . Reflections would cause the dot to be deflected to the left , creating a blip whose vertical location could be measured against a scale to determine range . The switch would then move to the next position and cause the right @-@ hand side of the display to be redrawn , but the signal inverted so the dot moved to the right . The switching occurred fast enough that the display looked continuous . 
