Clicker and Whistle 2 in 1
As a clicker When you press it, you will hear the short, crunchy,"gaoda" sound Communication tool, there was no scolding or punishment during the training, only to establish mutual trust, let them know how to think, to strengthen the hope they do.
As a whistle, you could use it to call a dog from a long distance, an ultrasonic wave that can call a dog back home