Question: What happens to the structure of the EFOCI (Outgoing Call Information) file within the USIM application after a call is disconnected, and what is the implication for its contents?
Option 1: The file structure is reset, and all previous call information is permanently deleted.
Option 2: The file's cyclic structure allows for updating its contents only after a call is disconnected, ensuring the most recent call information is stored.
Option 3: The file structure remains unchanged, but the entire file is filled with 'FF' to indicate disconnection.
Option 4: The USIM application automatically links the EFOCI to a new phone book entry after each call disconnection.
Explanation: This is correct because the cyclic structure of the EFOCI file, as specified in the 3GPP TS, implies that updates (i.e., storing new call information) occur only after a call has been disconnected. This mechanism ensures that the file always contains the most recent outgoing call details, such as time and duration, while efficiently managing storage by overwriting older records in a cyclical manner.