APP remote monitoring; wireless calling system can send real-time updates to your mobile APP; so you can stay informed of family member's condition and respond quickly to provide the best care Wireless mobile host; host is equipped with built-in battery; allowing you to move it without worrying about power; with this feature; you can ensure that you always receive a signal Expandable; the call button is expandable; up to 24 buttons; you can add more call buttons to meet the needs of various different usage scenarios Wireless function; even if you are in another city；your smartphone can receive alarm notifications from call button Low battery reminder; when the host battery is less than 20%; the APP will push a low battery prompt message;no need to worry about low battery Receiver Specifications: Size: 112.20mm*112.19mm*22.07mm Weight: Approx. 125.5g Color: White Shell material: white ABS Battery specification: 800mAh lithium battery Operating voltage: 3.7V-4.2V Wireless distance: >100m (test environment: open ground) Transmitter specifications: Size: 55mm*18mm Weight: 32.7g Color: white, blue Material: ABS Battery Type: Coin Cell CR2450