A mobile device user notices that the system update includes an update of the Primary Rate ISDN (PRI). What is the function of the PRI?

A mobile device user notices that the system update includes an update of the Primary Rate ISDN (PRI). What is the function of the PRI?

• It is the configuration of radio frequencies used on the device.
• It is the data rate setting of the user account with the carrier service.
• It is the configuration of the data rates between the device and the cell tower.
• It is the configuration information that the device needs to communicate on networks other than the carrier network.
  

  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.