【Excellent Design】433Mhz RF Self-generating Wireless Doorbell. You can install the doorbell receiver indoors and install the self-generating transmitter on your exterior door, allowing your visitors to remotely ring your indoor doorbell via the exterior door transmitter. Stable and reliable performance with high reception sensitivity. A strong signal can pass through walls, floors, doors etc. The controlled range is about 200m. 【Easy to install】 The plug-in bell receiver can be plugged into the socket in your home anywhere. And the waterproof kinetic transmitter can be installed on the exterior door. No wiring required. This kinetic transmitter has a small built-in electromagnetic generator coil. A small pressure on this transmitter can generate a current which powers it. No battery demands. 【Wide application】Products can be used in homes, farms, factories, offices, laboratories, supermarkets, etc. You will never miss a visitor.