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Review title: Whirl
Product review: I have three dogs, this works on one of them, doesn't seem to do a thing for the other two. One thing to check is push the test button on the unit. You'll get a red light but you should also barely hear a whirling sound as the unit spins up. I've had these where the light came on and no mechanism activating inside after a few weeks of use- that's a sign to return it for a new one. It advertised as inaudible to humans so you'll only hear it when within a few inches.
