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(a) Subject to paragraph (b), aerodrome control may verify the transponder level information of a departing aircraft when the aerodrome control situation display indicates a positive rate of climb from the aerodrome elevation.
(b) Transponder level information must not be used when the displayed level varies by more than 300 feet from the aerodrome elevation during the take-off roll.
Speed control must not be applied or continued after a point 4 NM from the runway threshold on final approach.