Engineered with special sound level and light intensity to scare away deer but remain unobtrusive to humans; Developed by a PhD plant scientist and found to be extremely effective in tests performed by Big Game Biologist with New York state's Department of Environmental Conservation; Wide angle of sensitivity, up to 25 feet from the unit, can protect an area or redirect deers' path of travel away from garden plants; Effective year 'round; simple battery operation means that you do not need to bring either water or electricity to area that you need to protect;