Wireless smart voice doorbell, talk with visitor via two-way voice intercom, which lets you know who visits your home and talk to them and let them know I'm coming, please wait.     1 receiver and 1 push button, talk between receiver and push button via wireless connection within a large range (outdoor bell: 200m, indoor bell: 5-50m without any obstacle), stable transmission signal to make voice clear.     Receiver support rechargeable battery, transmitter supports 3*alkaline battery last up to Approach 4 months (transmitter 3*alkaline batteries are not included).     It's widely used for office and house, get know who is outside, and convenient for the elder who needs much more time to open the door, very practical. With 15 different ring tones and 3 levels adjustable volume.     Easy to install and use, visitor presses the outside doorbell, after getting ring, you should press the button one time on receiver to get connected and then hold to speak, release it after finishing.     Indoor unit input voltage: 5V 1A     Outdoor unit power supply: 3*alkaline battery (1.5V*3) (not included)     Indoor unit power supply: Built-in lithium battery(included)     Wireless frequency: 467MHz     Ring Tone: 15 Options     Volume Range: 3 Levels     Transmission distance: outdoor bell:200m; indoor bell:5-50m (without any obstacle)     Waterproof: NO waterproof function     Operating temperature: -20℃ to 55℃     size:16.3 x 14.5 x 4cm      Material:ABS     colour:Black / White          Package Contents:      1 x Indoor Unit     1 x Outdoor Unit     1 x Screwdriver     2 x Double-sided Adhesive     1 x USB Charging Cable          Only the above package content, other products are not included.     Note: Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.