The Spray Barrier has 2 components: an emitter dish and a spray receiver collar. The emitter dish plugs plugs into your mains supply. It generates a low frequency radio signal that is transmitted in all directions. As your pet approaches the emitter dish, the spray receiver collar will pick up the signal. The collar will at first emit a warning beep to let your animal know it has reached the limit. Should he continue on, he will then receive a brisk spray of citronella. The protected area has an available radius of 2 - 10 feet (0.6 to 3m).