This is a scientifically proven device to remove cats from your garden and other environments. It has had extensive testing and has been approved for use by the Royal Society of the Protection of Birds as a humane means of deterring cats from areas wild birds frequent. It is a battery operated and takes a high capacity 9v battery. On average a good quality battery will last 2-3 months. When power Is running low the automatic power checker will let out a series of audible bleeps alerting you that the battery needs changing. It has a range of 1350 sq feet, which is approximately twice the range of other brands on the market today. It is also more efficient, neater and cost effective compared to various chemical sprays, gels and pellets on the market that need constant re-purchasing and re-application after every rain shower. It also maintains functionality during poor weather conditions and can operate at -30c to +60c. Cats have a range of different behaviour responses to the ultrasonic waves, some will instantly flee, but it is also possible some will choose to lay down near the device in protest to being forced out of the area. However, this protests usually does not last long as they cat will soon find out this is a battle that can#t be won. It is a dark green small device and comes with a stake to place easily into the ground and can be repositioned as required.