Self Generating Wireless Doorbell: No wiring, no battery, one press to convert kinetic energy into electric energy, transmitting wireless signal, no need to worry about changing the battery for the doorbell.Long Distance up to 100meters open space. Two transmitters and two receivers design, can be used in double door and double decker houses, and can set a separate corresponding ringtone.It’s also a pager. When a baby and the elderly sleeping alone, and pregnant women need help, they can press it, effectively protect your family.