All GSM GPS beacons need a SIM card to work. 

Before you buy a SIM card...

If a GPS beacon in itself already allowsget the geographical coordinates it will also record them on the device for later consultation. SIM cards allow you to send your data to a recipient via SMS and send the information to the server of theGPS tracker mobile app. No need to wait, the information is real-time. 

M2M SIM cards 

M2M SIM cards, an acronym for Machine to Machine, are SIM cards specially designed for electronic devices. Aside from the GPS tracker, these cards are generally used for alarms of all kinds. They are multi-operator SIMs: they switch from one operator to another in case of problems. Although it has the advantage of rarely being in short supply of telephone network coverage, subscription to this type of SIM costs a little more than for a conventional SIM card. This card is available from telephone operators and some specialty stores. 

Classic SIM cards

The SIM cards generally used for our phones and smartphones are well suited to the transmitting geolocation data from a GPS beacon. These are the sim cards most used for the use of a GPS beacon. You can choose between a prepaid sim card (for irregular uses) or a phone subscription (for more intense use). Most, if not all, tags require SIM running on the GSM network, i.e. a 2G SIM. This is a fairly old model, since it dates from the 90s, but the tracer requires this specificity. All you have to do is pay the operator a subscription to allow the SMS service.