If you bite people indiscriminately, will you corona?

If an old man or a girl keeps a giant dog and the dog suddenly goes mad, you will thank the design, but there are also many problems.

Some cruel, don't raise will not scream

This design is not friendly to dogs. In addition, there is no difference between just talking about modeling and not talking about functional principles and not designing.

For the first time, I know that there is such a device that keeps dogs from barking. What is the principle?