Explanation:

In addition to mobile operating system updates, there are two other types of updates for mobile device radio firmware. They are called baseband updates and consist of the Preferred Roaming List (PRL) and the Primary Rate ISDN (PRI). The PRL is configuration information that a cellular phone needs to communicate on networks other than the carrier network. The PRI configures the data rates between the device and the cell tower. This ensures that the device is able to communicate with the tower at the correct rate.