Why does the 3g gps tracker need to install a SIM card?

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 instantly according to the mobile phone or computer. The location of the car where the gps tracker is installed. It is very likely that it is not very clear to see the text, then use the picture to show:

Looking at the photos, do you know how positioning works? As shown in the figure, 3g gps tracker needs to transmit the data received by the device to the server in the process of positioning and tracking. Only after this step can everyone see the location, and how to transmit this information? , then use the SIM card.

As we all know, the SIM card has a communication function, and the medium of this transmission is usually called traffic, that is, GPRS. If the SIM card is not added to the 3g gps tracker, the positioning information cannot be transmitted to the server, and everyone cannot see the location of the car on the map.

If friends who are usually concerned about 3g gps tracker are likely to have heard of 3g gps tracker without a card, then what is this device based on to transmit data?

In fact, this so-called card-free 3g gps tracker doesn't mean that you don't need to install a SIM card, it's just that the SIM card chip is directly attached to the PCBA board (that is, the motherboard) during the production process of this device, so External publicity is also a card-free!

Having said so much, I should understand why the 3g gps tracker needs to install a SIM card.

3g gps tracker https://www.eelinktracker.com/3G-GPS-Tracker/