 This led to Hanbury Brown 's work on the Mark IVA , which differed from the Mk . IV primarily by having an additional display unit in front of the pilot . The radar operator had an additional control , the strobe , which could be adjusted to pick out returns at a particular range . Only those returns were sent to the pilot 's display , resulting in much less clutter . Unlike the operator 's display , the pilot 's showed the target 's location as a single dot in a bore @-@ scope like fashion ; if the dot was above and to the right of the centre of the display , the pilot had to turn to the right and climb to intercept . The result was what was known as a flying spot indicator , a single selected target showing a direct indication of the target 's relative position . 
