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.
For charging two Dogtra electronic devices from one power source. By using 2 "Y" Splitters, you can charge 3 devices from one power source. (Two 2.1mm coax power plugs connected to one 2.1mm coax jack)