The Shake&Vibrate(TM) Bed Shaker is designed to alert a sleeping, inattentive, or hearing impaired person by its powerful vibration. This reliable device is easy to use, and very effective. The Bed Shaker can be used directly with the DryBuddyFLEX bedwetting alarm system to help wake the sleeping user. It plugs directly into the socket at the back of the DryBuddyFLEX transceiver, and will be automatically turned ON or OFF with the alarm in the transceiver. To wake a sleeping user, place the bed shaker under the sleeper's pillow, or between the bed mattress and its box spring. It requires a 12V DC 500mA power source. DO NOT get this device if you do not have a proper power source. Attach/plug it to any 12V DC alarm device using its 2.5mm x 5.5mm barrel plug. The power cord is 2 meters (78 inches) long. No batteries are needed. When the alarm device is activated, the vibration is felt by and alerts the user. NOTE: This Bed Shaker alarm can be used with a 110V-120V AC power source by separately purchasing the DryBuddy 120V to 12V DC 500ma Power Supply. This Power Supply has a barrel socket into which the Bed Shaker?s barrel plug will fit. The Power Supply can then be plugged into an 110V-120V AC 60Hz power source (such as the electric line in a house in the U.S. and Canada) which is switched by an alarm device or separate power switch. There is no power switch in the power supply. This Power Supply can be found on Amazon by searching for DryBuddy DB-PS120 . Note: This bed shaker requires a 12V DC 500ma power supply to work properly. Please verify that your alarm device will provide this power, else the bed shaker will not work properly. Help Amazon by keeping reviews honest, trustworthy and sensible. Thank you.