Features:*Wirele 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.*1 receiver and 1 push button,talk between receiver and push button via wirele connection within a large range(outdoor bell:200m indoor bell:5-50m without any obstacle),stable transmiion 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 prees the outside doorbell, after getting ring, you should pre the button one time on receiver to get connected and then hold to speak,release it after finishing.Specifications:Indoor unit input voltage: 5V 1AOutdoor unit power supply: 4*AAA battery (not included)Indoor unit power supply: Built-in lithium battery(included)Wirele frequency: 467.6375MHzTransmiion distance: outdoor bell:200m indoor bell:5-50m (without any obstacle)Waterproof: NO waterproof functionOutdoor unit working time: 4 months(Approach)Indoor unit working hours: 48 hours(Approach)Color: SilverMaterial:Plastic+ABSOperating temperature: -20 to 55Package Information:Package Size: Approach.16.2*11.8*2.4cm/6.38*4.65*0.94inPackage Weight: Approach.155g/5.47ozPackage List:1* Indoor Unit1* Outdoor Unit1* Screwdriver2*Double-sided Adhesive1*USB Charging Cable1*User Manual(English)