Initially the method of calculation involves assessing the abundance and distribution range of a non-indigenous species (NIS) for a specific area (this can be, for example, an entire regional sea, bay, inlet, lagoon, pond, lake, marina, a sand bank, an aquaculture site etc.).
Press the Menu on your Sprint phone's home screen. Select Settings and press the Menu key. Press the Menu key. Scroll down and highlight the PRL field and press Update. Wait for the update to complete. Press the End key to exit to the phone's home screen.
The current PRL for the iPhone 5 is 51095. The only difference by market is actually written into the PRL, and in basic terms your phone will recognize what geographic zone you're in (Chicago for example) then apply the roaming rules for that geographic zone that are written into the PRL.