Features: *Wireless smart voice doorbell, talk with visitor via two-way voice intercom,which let you know who visits your home and talk to them and let them know I'm coming, please wait. *2 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 4*AAA battery last up to Approach 4 months(transmitter 4*AAA 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. *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. Specifications: Indoor unit input voltage: 5V 1A Outdoor unit power supply: 4*AAA battery (not included) Indoor unit power supply: Built-in lithium battery(included) Wireless frequency: 467.6375MHz Transmission distance: outdoor bell:200m indoor bell:5-50m (without any obstacle) Waterproof: NO waterproof function Outdoor unit working time: 4 months(Approach) Indoor unit working hours: 48 hours(Approach) Color: Silver Material:Plastic+ABS Operating temperature: -20 to 55 Package Information: Package Size: Approach.16.2*11.8*4.8cm/6.38*4.65*1.89in Package Weight: Approach.263.5g/9.29oz Package List: 2* Indoor Unit 1* Outdoor Unit 1* Screwdriver 3*Double-sided Adhesive 2*USB Charging Cable 1*User Manual(English)