Aetertek&reg; Updated & Submersible Dog Training Collar 918C Dog Training Shock Collar Rechargeable Dog Collar with 600 Yards Remote Range Vibration mode is strong enough to get your dog's attention....here are the steps to sync the remote: 1. Turn off all the receivers. 2. Choose dog 1 of the remote and then turn on 1 receiver and then press any function button (beep, vibrate or shock). Once synced successfully, receiver red light will be off and there will be a flash blue light. 3. Choose dog 2 of the remote and then sync the other receiver with it like the above step. &#x2605;Rechargeable 100% waterproof collar receiver, can be immerged in water when your dog is swimming with it &#x2605;Remote control 600yards (approx. 550 meters) and signal can pass through walls and fences, suitable for all dog size from 15-150lbs &#x2605;As 1 or 2 dog training system, this list is for 2 dogs trainer, for nippy dog by serious user &#x2605;Popular dog bark collar provide professional and safe correction mode: Auto anti bark, Flashlight, Vibrate, 0-9 level adjustable Shock, Beep, sleep mode for more battery life