1, simple and easy to use: the wireless doorbell installation is convenient, no wiring or drilling, will not damage your door 2, wide range of ringtones: the doorbell with horn increases sound quality, doorbell coverage of 200 square meters 3, no need for power supply: self-powered electric doorbell without battery, self-powered electric design, explore the revolutionary inter-era reform 4, don't worry about power outages: excellent wireless doorbell, no longer worry about the doorbell not ringing without batteries when friends arrive 5, working principle: the built-in doorbell generates a pattern, when you press the keys with your fingers, it is automatically converted into electricity, instant wireless signal, the indoor receiver rings automatically Specification Item Type: Self-Powered Wireless Doorbell Material: ABS Color: Black Weight: 111g / 3.9oz (Approx.) Package Contents 1 x Doorbell 1 x Receiver 1 x Back Adhesive 1 x User Manual