DT Systems IDT-PLUS Micro Dog Trainer Collar Receiver and Transmitter Expandable to 2- or 3-dog system with micro-idt add-on collar units (sold separately) with up to 900 yard range Positive vibration as well as 16 adjustable intensity levels of momentary (nick') stimulation and continuous stimulation and gentle touch system extra mild stimulation Lightweight, compact, completely waterproof collar and transmitter with rechargeable ni-mh battery system and built in safety shut-off system Maxx-range internal antenna system in collar belt smartled light on collar receiver Weather resistant transmitter Expandable to 3 dogs with Add-On Collars Up to 900 yard range Weather resistant transmitter Built-in safety shut-off system