The 1800 can be expanded to control up to 3 dogs by adding SportDOG Brand® Add-A-Dog® collars. With a long 3/4 mile of range and the comfortable "Soft Coat" Transmitter finish, this unit is a pleasure to handle. Dog Training Gear the way you'd design it. 3/4 Mile Range Receiver and Transmitter are waterproof and submersible Expands to 3 Dogs Up to 16 levels of continuous and momentary (nick) correction Tone only button Tone only for 1 sec, then stimulation, option. Replaceable,rechargable NiMH Batteries in both transmitter and receiver Low battery indicators in both transmitter and receiver 40-80 hours "on time" between charges Lanyard Belt Clip Lifetime Limited Warranty