Add another dog to your current SportDOG Brand® electronic collar system or replace a lost collar receiver with the SDR-AX Add-A-Dog® Receiver for the SportHunter® 1825. Compatible with SD-1825/1825X, SD-1825CAMO, SD-1225, SD-3225 and SD-2525 systems, the SDR-AX Add-A-Dog® Receiver comes with a convenient docking station that charges the collar in 2 hours.