Baby Sound Monitor Wireless Phone App Remote Monitoring Infant Care Two Way Intercom with Night Light Item Type: Baby MonitorMaterial: ABS + Electronic Components Main Unit Battery Type: Lithium Battery (included) Main Unit Battery Capacity: 1000mAh Subunits do not contain batteriesSound Monitor Size (Main Unit): Approx. 10.5 x 7 x 5cm / 4.1 x 2.8 x 2 inches Sound Monitor Siz (Sub Unit): Approx. 10.5 x 7 x 5cm / 4.1 x 2.8 x 2 inches For best results, charge the main unit before use. After initial charging, charge normally as required.The main unit can be operated normally with the power adapter already plugged into the unit with the battery installed. 2. Press and hold the power On/Off button for 2 seconds to turn on the main unit. The power LED indicator will illuminate green to indicate 3. Once both the sub unit and main unit are turned on. The main unit will transmit the sound captured by the sub unit. 4. If there is no link or you are out of range, the sound will turn off and the main unit will beep rapidly after failing to re establish the link. Move the main unit closer to the sub unit until the link is re established. 5. Press and hold the power button to turn off the main unit.