Question: During a call, with one call already on hold (initial call), what action allows the User Equipment (UE) to switch back to this held call from an active second call, assuming no other waiting calls exist?
Option 1: Enter the initial directory number followed by SEND
Option 2: Enter 1 followed by SEND
Option 3: Enter 0 followed by SEND to clear the current action and automatically switch
Option 4: Automatically switches after ending the second call with END CALL
Explanation: According to specified procedures for managing multiple calls on a User Equipment (UE), entering '1' followed by SEND is the designated action to clear an active call and return to a held call, provided there are no waiting calls. This sequence specifically toggles between the active and held states when only two calls are involved, making it the correct choice for switching back to the initially held call.