How Do They Communicate?

The dogs are trained for either detecting the explosives or narcotics, but not both. Why is that? The reason is that dogs can’t communicate with the assigned officer about the material it had found. And if the dog is trained for a specific task then there would be no confusion about the material it has found because a narcotics trained dog would only be able to detect narcotics and the dog which has been trained to detect the explosives items will only be able to detect those which helps the police to take actions accordingly. Did you know why police dogs are trained in German commands?