signal transmission. 2.Please choose the positive contact protruding Lithium batteries. 3.It is recommended to purchase an additional doorbell chime to hear the sound of the doorbell more clearly. 4.If you are outdoor, you have to connect doorbell with home WIFI, so that you can check the doorbell working state with your phone. Meanwhile, you can also receive the information which comes from the doorbell. Overview: This wifi doorbell can connect home WiFi and achieve a two way intercom between the doorbell and cell phone. When a visitor presses the doorbell, sound is activated and the camera will start sending real time call to the cell phone. The user will receive the call and can check who the visitor is, can intercom with the visitor. It can make your life easier, smarter and safer. It's highly cost effective! Specifications: Visual Angle: 166 Picture Resolution: 1080P Coded Format: H.264 #43; Battery: 2 * Lithium Battery (not included) Standby Power: 20uA Working Power: 170mA Standby Time: about 8 months PIR: support IR: support Night-vision: support Photosensitive: support Built-in WIFI: support 802.11 B/G/N Mobile Phone App: TuyaSmart support IOS Android Alarming Reaction Time: 3-55 seconds Record Method: manual, doorbell trigger, motion detect. TF Card Storage: Up to 32G TF card storage(not included) Cloud Storage: Support Material: ABS Color: Black Environment: -10~50 Working Humidity: lt;95% Item Size: 138 * 50 * 26mm / 5.4 * 2 * 1in Package Information: Package Size: 15.1 * 8.5 * 4.7cm / 5.9 * 3.3 * 1.85in Package Weight: 195g / 6.9oz / 0.43lb Package List: 1 * Wifi DoorBell(without batteries) 1 * Bag of Mounting Screws 1 * User Manual (English)