Rechargeable remote transmitter and collar-receiver. * Four modes(static shock/vibration/beep/light) at your disposal. * 100 intensity levels of vibrations/static shocks are adjustable. * Easy to sync the remote transmitter with the collar receiver. * The system can be used with 1 or 2 receivers. (The additional receiver should be the same type as your previous one and please search "B00EN9W9GC" on Amazon for puchase)