The Petsafe PBC00 12788 Deluxe Outdoor Bark Control can be programmed to turn the unit on and off at specific times. An internal microphone picks up the barking sound and the unit gets activated. It emits an ultrasonic sound, which cannot be heard by most humans, similar to a dog whistle.
The PBC00 12788 is a helpful device that controls dog barking with in the range. It detects bark up to 50 feet away and has two color LED for good/low battery indication.