To understand how most trackers work, it's important to know the distinction between an active and a passive GPS tracker. Passive trackers, also known as GPS loggers, take the information transmitted from GPS satellites and store it, with no means to transmit the data. To access location and speed information, the user needs to retrieve the GPS tracker and either plug the device into a computer or plug a SIM card into a computer to see the data. Active trackers, also known as real-time trackers, contain GPS satellite receivers in addition to cellular transmitters which enable the device to take in location information and transmit it as it happens.
As they're the only devices affected by changes to the cellular network, we’ll be discussing active trackers exclusively below.