On Dog Star Daily Rachel Friedman has posted a video in order to explain calming signals. The dogs are really cute so it's fun to watch.
First of all, there is no intention in a dog to calm another dog. Watch the video and see if you can see the universal "force" of attraction, the two dogs then becoming a mirror to each other (like-is-attracted-to-like-----but only opposites-can-connect). Which dog is at the Predator pole, which dog is at the prey pole (emotion ALWAYS flows in this direction)? Which sense allows them to acquire an emotional ground and connect? What happens to the energy in the jaws of the dog at the predator pole? What part of its body does it first get displaced to in order to make contact when the dogs begin to get really excited, and then where next in that dog's body does the energy get channeled into? What is the dog at the predator pole trying to do when it feels safe to make full contact? In this vein can you see how sexuality/sensuality allows the Predator/Prey emotional dynamic to evolve into playfulness?
Now if we were to next ask what is each dog feeling so that their interaction is organized in this way, we would arrive at the true meaning of "calming signals." Resolving this question elucidates the universal principle of emotional conductivity that serves as a template for all animal interactions, no matter the species, no matter the context.