A guy in Utah makes a squealer that has a photo cell in it and will only come on at dusk, then turn off as it gets daylight. You can put duct tape over the photo cell eye and it will run constantly. I'm not sure if I'm spelling it correctly, but the name to google is Wasatch??? I have two different models they make. One is programable as far as sound and length of sounds, the other just has a squealer (rabbit I believe), and you can adjust the length of the sound it emits by a couple of different settings. I didn't use them this year as I only trapped for a short time and was near areas where others frequent. I believe that using them in these types of areas only serve to let people know where your trap is and you take a chance of theft. I think if you were to use them in a spot and back away fifty or so yards, you would benefit more from their use. I've heard that some predators are a little wary about coming right into them, but others say that isn't so. You would have to do the trial and error thing to see how they would best work for you in your area.