Topic: 3g gps tracker

Why does the 3g gps tracker have to add a SIM card to the tracker if it wants to track and locate the car, what is the reason? First of all, let's briefly understand the working principle of the positioning and tracking of the 3g gps tracker. In fact, the working principle of 3g gps tracker is relatively simple, that is, the locator receives the information sent by GPS satellites, and then transmits this information to the server on the ground for analysis, so that everyone can view 3g instan...