Wireless Doorbell One For Three AC DC Digital Features and specifications: 1.Press the button, super learning code can freely learn to match, can be unlimited matching receiver and button. 2.The transmitter without screw chuck design to achieve waterproof and dustproof. 3.The transmitter USE a 23A12V alkaline battery (not included battery). 4.The receiver uses 3 AA alkaline batteries, no need to plug in the power supply, and the battery can be used.(not include battery). 5.Receiving distance:300 meters in open area. 6.The wireless signal will be affected by obstacles. The more obstacles, the more serious the signal loss. 7.Receiver has 6 levels(can be mute) 0-80db,48 music to choose from. 8.Transmitter size:79*45*22mm 9.Receiver size:110*57*25mm 10.Just plug the receiver into an electrical outlet,the push button transmitter can be stick it to the door with provided adhesive tapes.