Whistle ultrasounds for dogs

This application is a dog whistle dog but adapted to current technology.
Dogs are particularly sensitive to frequency (Hz) high. Some of them they can not be heard by humans. Professional trainers often use this whistle.
The dog whistle is a particularly effective way to respond dogs. Led the dog understands what his master wants, and performs its task. The dog whistle to the advantage of a very good control of the dog without disturbing people around.
This application is compatible with all races.
There are around 400 breeds of dogs in the world and therefore different ears. To overcome this contradiction, 13 different ultrasonic frequencies are available.