Translation of "Negativanzeige" in English

Wenn das nicht der Fall ist, soll der Hund eine "Negativanzeige" machen, das heißt, er soll seinem Hundeführer signalisieren, dass er keine Spur der Person, deren Individualgeruch am Geruchsträger war, ausmachen kann.
If this is not the case, the dog has to indicate a 'negative', in that he has to tell his handler that there is no trail of the person whose individual scent was on the 'scent carrier'. 'Negatives' are evidenced by the dog's body language that he has run out of scent.
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