The Wi Fi Waterproof Collar Transceiver is extremely small at 2.5"" in width, 1.5"" in tall and only 1.25"" deep. It only weighs 2.3 ounces, yet is packed with advanced electronics. The collar can be preset to one of 4 fixed static correction levels or a Progressive Correction setting. When approaching the preset boundary the collar emits a warning tone. If your dog continues to approach the boundary the preset correction level will be triggered. If you have selected setting 5 then Progressive Correction will be triggered. Progressive Correction starts at the lowest level. If your dog continues toward the boundary the internal microchip will continually increase the correction level based on the speed your dog is approaching the boundary and the distance your dog is away from the boundary. You can monitor this from your Smart Wi-Fi Base Station. In a multi-dog system, each collar can be independently programmed allowing you to customize your system for the temperament of each dog. Should your dog leave the Safe Zone the Correction will halt after 30 seconds. The Perimeter Wi-Fi Pet Fence includes a battery charger built into the Transmitter-Base ""Smart Station"" and two rechargeable batteries. Just put the fully charged battery in the collar and the drained one in the Smart Station. The Base Smart Station charges the battery while it monitors the charge level of the battery in the collar. When the battery in the collar gets low, take the fully charged battery from the Base Smart Station and replace the battery in the collar -- save money not buying replacement batteries. Battery recharge time normally takes 3 - 4 hours. When the battery in the Smart Base Station is fully recharged, it will act as a battery backup for 8 hours should the household power go out. This safety feature allows for continual safe operation and containment of your dog. NOTE: This product may not be used around a metal roof, large metal structures, or buried wires.