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 work insert 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.