Kaito Wireless Doorbell No Battery Needed for both receiver and transmitter, Battery Free Door Chime with 25 Ring Tones, Waterproof, Synchronize and Work in Pairs, Easy Setup This is a Wireless Door Bell, but No more battery needed or Worry battery runs out ! By pressing the push button, it converts kinetic energy into an electrical signal to ring your wireless doorbells. So no more worrying your push button runs out of batteries and no more hassling in buying awkward weird batteries to run your push button. You will always be able to hear your doorbells ring! Do not need any battery or power line to charge the transmitter, and it transforms 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 70 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.