The Dogtra combines our most versatile 1900S e-collar with a compact Dogtra HANDSFREE SQUARE, which allows you to control a transmitter remotely. This 2-dog system provides the flexibility and versatility needed to multitask and be discreet in any situation. Whether you want the option to instantly have different functions at your fingertips, have a family with multiple users to care for your dog, or are a trainer working with a new client, the can be used for a diverse range of training scenarios through the expandable HANDSFREE SQUARE. Each SQUARE can be paired to different functions and allows many users to quickly access any feature, at any time within 33 feet of the transmitter. with comfort and safety in mind, the 3/4-mile range is IPX9K waterproof certified making it durable and reliable for demanding training conditions. In addition to the easy hands-free access, the also offers 127 stimulation levels to choose from for accurate control, HPP (High Performance Pager) vibration, and an ergonomic receiver shaped to the dog's neck. HANDSFREE SQUARE for Remote Control Expandable up to 14 HANDSFREE SQUARES 3/4-Mile Range IPX9K Waterproof Certified 127 Stimulation Levels/Rheostat Dial/LCD Screen Nick/Constant Stimulation & HPP (High Performance Pager) Vibration Enhanced Contact Points For Dogs as Small as 35 lbs 2-Hour Rapid Charge Batteries High Output Receiver