Question: What is the purpose of the in-call modification procedure in a circuit switched service?
Option 1: To allow users to switch between different call modes during the same call, potentially changing channel configuration parameters or allocating a new channel.
Option 2: To enable users to use multiple information transfer services simultaneously during the same call.
Option 3: To facilitate handover procedures between different base stations during an ongoing call.
Option 4: To modify the repeat indicator for mode changes between alternate and sequential modes.
Explanation: The in-call modification procedure is used to change from one call mode to another within the same call, which may involve changing channel configuration parameters or allocating a new channel. This allows users to use different information transfer services during the same call, but not at the same time.