Bark collars can be a quick and simple training tool for barking dogs.
An electronic bark collar is activated by a dogs bark which creates the vocal chords to vibrate and sets of a static shock, (no different than walking on a carpet and touching your friend) that is just uncomfortable enough to stop his unnecessary barking but doesn’t harm him.
You can also consider a citronella bark collar. The citronella bark collar releases a spray of citronella in front of the dog's snout when the citronella bark collar registers a bark. Your dog hears it, sees it and most importantly, smells it. At the first spray of citronella, your dog's natural curiosity will be to seek the origin of the new odor. The dog will very quickly learn that when he or she barks, the Citronella Bark Collar Sprays! Through this harmless conditioned reflex, this discourages your dog from barking.
Lastly there is the ultrasonic bark collar that emits a high pitched sound when the dog barks. This startles your dog and distracts his barking and discourages him from continuing.