... will reply "OK" if succeeded. If only set one sos number, it can be as follows: SOS, ... D,1,2,3,4# (D means delete one sos number) For example: SOS, D,1# ... delete the third number If delete several numbers at one time, SMS command can be: SOS, D, ... GPS positioning. The precision is aroung 10m. Notice: The sim card should activate GPRS function. GTK920 Automatic positioning package, gps tracker locator ...