AGPtek Rechargeable Remote Pet Dog Training System with 2 Collars(Please note that every time you pull out the batteries, you need to match code again 100 levels of vibration. 100 levels of static. The levels can be altered by use of up & down button. The system can be used for 2 receivers. Convenience of easy-to-read LCD screen shows the stimulation level. We would like to suggest you to match code before using it and please be noted that you need to adjust the mode to the responding item. For example, if you want to shock, you should adjust to the shock mode. Besides, you are advised to adjust to 80-100gears for the big dog, but for the smaller dog, it should be 50 gears. And if the gear is too lower,there will be no reaction. Note: you are kindly suggested to plug the usb into the computer for charging. But if you make use of charging connector, please make sure that the voltage of charging connector is under 5V, 1A. Besides, please never use your Blackberry cellphone connector to charge our collar. and iPad, GALAXY Tab, Kindle, PSP are NOT applicable.