How it work: An internal microphone picks up the sound and the unit is automatically activated. The bark control collar starts with emitting an ultrasonic sound of 1 second as a warning at the first bark. At the second bark the collar emits an ultrasonic sound of 2 seconds. From the third bark the collar emits a 3 seconds ultrasonic sound and gives 2-3 seconds static shock. The dog should stop barking. If the dog barks within 1 minute after the first static shock, the collar sends out a 3 second ultrasonic sound and 2-3 second of static shock. If the dog stops barking, the collar resets itself to the lowest level and repeats the first 3 steps. The shock levels can be adjusted with the delivered screwdriver. Specifications: Usage: Training & behaviour aids Powered by: 2 * AAA batteries (Not included) Collar material: Nylon Adjustable collar strap length: Approx. 36cm-48cm / 14.2-18.9in Bark controller size: 7.7 * 3.5 * 3.8cm / 3.0 * 1.4 * 1.5in Bark controller weight: 73g / 2.6oz Package size: 9.5 * 9 * 4.7cm / 3.7 * 3.5 * 1.9in Package weight: 117g / 4.1oz Package including: 1 * Bark controller 1 * Collar strap 1 * Test light 1 * Special screwdriver 1 * User manual