New creative design: battery-free wireless doorbell. * Do not need any battery or power line to charge the transmitter, and it can transform its own mechanical energy to electrical energy by pressing the button on it. Do not need any wire for installation, easy and convenient to use. * Transmitter can be used in both high-temperature and low-temperature environment: from -40 to 60 Celsius degree. Transmitter is made of ASA plastic, durable to use. * Waterproof transmitter: can stand against heavy rain. Receiver is made of ABS plastic, inflaming retarding and environmental protection. * Long wireless transmission distance: up to 160 meters (no obstacles, in open field). Easy operation: the transmitter can be fixed on the wall by screws or adhesive pad and the receiver can be inserted to the power socket. 25 different polyphony ring tones for your choice.