Split screen
From Wiki 24
The split screen is a technique used to depict multiple scenes occurring simultaneously. It is particularly useful to show two sides of a phone conversation.
In 24, the split screen technique receives thorough use due to the show's real time format and simultaneous multiple plotlines. A split screen showcasing multiple characters and locations is always featured along with the ticking clock on each return from a commercial break. Additionally, the final few minutes of almost every episode are prefaced by a split screen, often with urgent music, to update viewers on the status of each major character and plotline as the hour ends.
Due to the expected nature of the split screen in 24, sometimes even the lack of a split screen can be used to create intensity, as was the case leading up to Ryan Chappelle's execution during Day 3 6:00am-7:00am. Without the split screen to signal the end of the episode approaching, it would be easy to hold out hope of saving Chappelle's life, until the clock signaled otherwise. While the final split screen sequence was used in virtually every episode during the early seasons, later on it became omitted more often. Other examples of episodes which do not feature a final split screen include Day 2 10:00pm-11:00pm, Day 4 10:00pm-11:00pm, Day 4 2:00am-3:00am, Day 4 3:00am-4:00am, Day 5 5:00pm-6:00pm, Day 5 7:00pm-8:00pm, Day 5 9:00pm-10:00pm, Day 5 6:00am-7:00am, Day 6 4:00am-5:00am and Day 6 5:00am-6:00am, most of which do so along the same line of reasoning. In the case of Day 4 10:00pm-11:00pm for example, the lack of a split screen caused us to wonder if maybe Jack would talk Mitch out of what he was doing and save the President's plane.
