Xexun TK102-2 Quick Start Manual page 23

Overtheairupdate*.
We will update software, if you need update tracker,
please install memory card (TF), and send SMS
"123456ldu,server=http://www.cnjeo.com/down/vpj.
bin,en=72". After you receive 3pcs of related
message, it means updated successfully. Notice： Need
about 5 min to do updating.