The Bird Barrier Bird Gard 110v Pro 2 (sd-bg42) is programmed to send a warning signal and predator calls to alert other birds in the area. It effectively repels birds like blackbirds, grackles, crows, cormorants, hawks, ravens and others. The product is programmable and have an on and off feature and a volume control for your convenience. A time-off sound and a 24 hour day and night switch is also a feature that helps you program the unit. It's ideal to install and place in small areas to block flocking birds away from your house and building. This product is available in two models and can be plugged into a 110 volt power outlet.