The Dogtra Extra Receiver features two sound modes authentic mallard duck-call attention getter or a beep-locater sound. The receiver can operate two launchers with the use of a 15 foot jumper cord. The Dogtra extra receivers are water resistant and are programmable, so you can start with a smaller system and later add launchers without having them specially built to match your system. Features: Multiple Sound ModesRealistic Duck Call For Retriever TrainingBeep Sound is Handy For Locating The Launcher1-Mile RangeAdvanced 2 Port System so You Can Run 2 Launchers Off 1 ReceiverWater Resistant ReceiverUser Friendly CodingAdd Extra Receivers & Match Them Anywhere, Any TimeLong Lasting Rechargeable Ni-MH BatteriesMulti Colored LED Light Battery Life Indicator Includes: Receiver (1)Battery ChargerCode Setting GuideNumbering Stickers