Question: In a Public Land Mobile Network (PLMN), what is the primary purpose of the Number Plan Indicator (NPI) in relation to the Called Party Address?
Option 1: To specify the geographical location of the called party.
Option 2: To determine the type of User Equipment (UE) used by the called party.
Option 3: To indicate the numbering scheme (e.g., ISDN/Telephony E.164, X.121, etc.) of the called party's address.
Option 4: To authenticate the identity of the calling party.
Explanation: The Number Plan Indicator (NPI) is crucial for identifying the specific numbering scheme or plan used by the Called Party Address. This distinction is vital because different number plans have unique formats and requirements for routing calls or messages correctly within a PLMN. By indicating the correct number plan, the NPI ensures efficient and accurate call setup and connection.