The range of operation is up to 460 feet* line of sight. It varies according to the position you are holding the Remote Control Unit, the weather, terrain, transmission from other radio devices, etc.
(* When there is a clear line of sight between the trainer and pet collar unit.)
Any obstruction between the trainer and pet collar unit will reduce the range significantly. When you are indoors with the trainer unit, the typical range is up to 100 feet.