Hello, this call anti-lost device is an upgraded 4G three-network universal device (supports China Mobile, China Telecom, and China Unicom mobile phone cards). After inserting the mobile phone card, you can make and receive calls. Supports common Android and Apple mobile phone download software on the market to remotely view positioning information. Support multiple mobile phones to download software to view location information. GPS remote precise positioning to prevent loss (5-meter positioning error in open spaces outdoors). Automatically answer calls, one-click SOS emergency alarm, fall alarm, low battery alarm. Electronic fence, activity track query. Alarm clock reminder, medication reminder, voice time telling. Track your steps during exercise to prevent harassment from unknown calls. The whole machine weighs 38 grams and measures 67*34*13 mm. It is compact, light and easy to carry. Free lanyard and keychain with order. Simple and easy to use, convenient for the elderly to use