This is Mini A8 GSM/GPRS/LBS Tracker Mini Global Real Time GSM/GPRS/LBS Tracking Device With SOS Button. The GSM/GPRS/LBS tracker is designed for use in any vehicle to track their location, such as caravans, boats, motor homes, trucks,for vans and construction machinery and many more - live tracking possibilities are limitless. This is particularly useful if your vehicle, pets, child or your belongings have been stolen. Time to enjoy the benefits this GSM/GPRS/LBS tracker brings!How does it workInsert 1 SIM card, after the LED flashes 3 times, the device starts.Phone number bind setting:If you need to authorize several mobile numbers at the same time (should be less than four), you can use a star key to separate them, for example: "SQ79609500000*SQ79608800001". Once the authorization is successful, the authorize mobile number will receive "Authorization success, Device XXX, password XXX,.Voice monitoring:Use the emergency contact phone number to call the device, it will enter the voice monitoring status.SOS Alarm:Press the SOS Button 3 seconds, it will call the emergency contact automatically.Call back function:Send SMS: 1111 to open the Auto-Call-Back function,Send SMS: 0000 to close the Auto-Call-Back function,When the sound around the device exceeds 60 decibels, the device will call the bound phone number automatically.