DT Systems H2O1820-PLUS Series Dog Training System, Black Up to one mile range; lightweight, waterproof collar and transmitter; maxx-range internal antenna system in collar belt; no-slip/soft-grip transmitter floats on water! 17 adjustable intensity levels of momentary (nick') stimulation and continuous stimulation; gentle touch system extra mild stimulation Dt systems' exclusive positive vibration feature ahs taken the dog training industry by storm, offering a positive and humane alternative to electronic stimulation. Expandable to 3-dog system with h2o addon collar units (sold separately) Rechargeable nimh battery system; built in safety shut-off system for improved battery life and reduced cost of operation Expandable to 3 dogs with Add-On Collars Lightweight waterproof collar and transmitter 16 levels of intensity, adjustable from the transmitter Built-in safety shut-off system