No battery needed, your finger to generate electricity, the transmitter has a built-in energy power generation module, and the doorbell to convert the mechanical energy into electrical energy to generate a wireless signal Rainproof and dustproof function, improved design of vertical structure rainproof, wind and rain not affect the use One thing with two purposes is not only a doorbell, but also can be used as a pager, a pager for the elderly, a pager for pregnant women, and a baby pager to protect your family when you are sleeping soundly at night Long-distance transmission has strong penetrating power, 150 meters long-distance transmission in an open area, and 30m long-distance transmission in a room. Innovative research and development of micro-energy harvesting generators, after 200,000 continuous tests to a long service life of the product Receiver size:78x54x20mm Transmitter size:66x40x20mm Color: As shown Material:ABS Plug Type:EU Plug,it applies to Indonesia, Germany, France, Spain, Italy and so on Voltage: AC220V Package Contents: 2 x Transmitter 1 x Receiver 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.