SportDOG FieldSentinel Add-A-Dog Electronic Training Dog Collar - The original collar for the SportDOG Brand FieldSentinel Series with BodyGuard technology – the world’s first e-collars with health alerts. Only compatible with FieldSentinel remote trainers. Add another dog to your current training and health monitoring system or replace a collar with the FS-AD Add-A-Dog Collar. The collar that comes with the FieldSentinel system is default paired to Dog 1 (toggle switch up). For the use of 2 dogs, the additional collar will need to be paired. Receiver battery lasts 140-160 hours per charge Fits dogs 8lbs or larger 3 types of stimulation - static/vibration/ton