The transmitter does not require batteries. the transmitter to generate electricity. Just the transmitter lightly to convert energy into electrical energy, and the doorbell can transmit wireless signals. Deep waterproof can also be used,safe and 38 kinds ringtones Four levels ofvolume Not only a doorbell but also a pager When the elderly,babies,and pregnant women sleeping alone have needs, the transmitter and ring How to Clear the pair code If the receiver is just pressed for l minute, and hold the buttonon the receiver, until the indicator light is on, then flash 3 times.all the code is cleared. (1)The receiver hasjust pressed the pairing button for seconds within 1 minute of power-on. (2)When the blue light on the receiver is always on.enter the pairing mode. (3) the transmitter, the blue light flashes on the receiver and the pairing is successful. Plug Type: EU Plug,it applies to Indonesia, Germany, France, Spain, Italy and so on. Voltage: AC220V Color:Black Material:Plastic Package Contents: 1x transmitter 1x receiver 1x screw pack 1x sponge sticker 1x English manual Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.