It’s easy to train dogs to do tricks or stop barking just with a whistle. They can hear sounds that humans can't since they hear sounds at much higher frequencies.

It's why we use specials whistle in order to get dog's attention. We use sounds between 14Khz and 20Khz.
Three modes are available :

* Manual : Touch the whistle to play the sound, when you stop touching it, the sound will stop.

* Continuous : Touch the whistle to play the sound, when you stop touching it, the sound will continue. You will need to touch it again to stop it.

* Timer : Switch to this mode to start playing the song for 5 seconds each 20 seconds. Leave this mode to stop it.

We're glad to help training dogs :)