The Vibra Call is a wireless system.The Lightweight unit is worn next to the body in order to feel the vibration and is either attached with built-in clip or placed in pocket. Transmitter sends signal to the unit - you then push all four of the buttons in order. Only the activated button will make the receiver vibrate a second time. Rechargeable 9 volt battery included. Must purchase separate charging unit to charge 9v battery such as the bat charger, stand alone charger or the sleep alert charger.5 Year Mfg Warranty.