Procter Dog Bark Trainer

PCBARK
This battery-operated device uses ultrasound to teach your dog not to bark. A sensor detects whenever the dog barks, and the Bark Trainer then emits a series of ultrasonic whistles, only audible to the dog
The dog will usually learn to associate barking with the unpleasant noise, which should reduce or even eliminate 'nuisance' barking.
Adjust the unit to react only to your dog's barking
Simple to use, and harmless to your pet
No harmful chemicals or pesticides
Battery-operated (3 x LR44, not supplied).
Average battery life 30-50 days